MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
19-6282; Rev 0; 7/12
Ordering Information appears at end of data sheet.
Simplified Block Diagram appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to www.maximintegrated.com/MAX77387.related.
*Patent protected PCT/US2008/075643.
General Description
The MAX77387 provides a high-efficiency solution for
smartphone camera flash applications by integrating a
dual-phase 2A PWM DC-DC step-up converter and two
programmable 1A high side, low-dropout LED current
regulators for flash and torch functions. An I2C interface
provides flexible control of the step-up converter, torch,
flash mode selection, and torch/flash safety timer dura-
tion settings.
The IC operates down to 2.5V, making it futureproof for
new battery technologies. The step-up converter features
an internal switching MOSFET and synchronous rectifier
to improve efficiency and minimize external component
count. Dual-phase operation ensures low output ripple
and provides smallest possible solution size. The IC also
includes dual high-side high-current regulators for sup-
porting torch and flash modes. The high-current regula-
tors can source up to 1A each in flash mode and up to
250mA each in torch mode. The high-current regulators
can be combined to drive a single LED up to 2A in flash
mode and up to 500mA in torch mode. The output volt-
age can be adaptively controlled, boosting only as high
as necessary to support the required LED forward volt-
age. Adaptive mode can be used in either flash or torch
mode and works with both DAC and/or PWM dimming
control schemes. This approach reduces IC power dis-
sipation by optimizing the boost ratio and by minimizing
the losses in the current regulators.
The IC includes control for external NTC, dual Tx mask,
flash strobe, and torch enable functions. This allows for
flexible control of the IC.
Additionally, the IC includes MAXFLASH 2.0 function
that adaptively reduces flash current during low battery
conditions to help prevent system undervoltage lockup.
Other features include shorted LED detection, overvolt-
age and thermal shutdown protection, and low-power
standby and shutdown modes. The IC is available in a
20-bump, 0.4mm pitch WLP package (2.1mm x 1.73mm).
Applications
Cell Phones and Smartphones
Tablets
Benefits and Features
S Input Supply of 2.5V to 5.5V with Full Functionality
S Dual-Phase Interleave Step-Up DC-DC Converter
True Shutdown Output
2A Guaranteed Output Current for VIN > 2.7V
and VOUT P 4.0V
Adaptive Output Voltage Regulation to Ensure
Industry’s Highest System Efficiency
Over 90% Peak Efficiency
3.125% Minimum Duty Cycle
Skip Mode Capable
On-Chip Power MOSFET and Synchronous
Rectifier
Up to 4MHz PWM Switching Frequency per
Phase
Small 0.47FH Inductor per Phase
S High-Side Torch/Flash LED Current Regulator
I2C Programmable Flash Output Current
(15.625mA to 1000mA in 15.625mA Steps)
I2C Programmable Torch Output Current
(3.91mA to 250mA in 3.91mA Steps for Non-
PWM dimming) (125mA to 1000mA in 125mA
Steps for PWM Dimming with Programmable
Duty Cycle from 3.125% to 25% in 3.125% steps)
Low-Dropout Voltage (80mV typ) at 1000mA
S I2C-Programmable Flash Safety Timer
S I2C-Programmable Torch Safety Timer and
Optional Disabled Torch Timer
S Dual Independent TX_MASK Inputs for Limiting
Flash Current During Tx Events
S Open/Shorted LED Detection
S NTC Monitoring for LED Protection
S Overvoltage Protection
S MAXFLASH 2.0 Preventing System Undervoltage
Lockup
S Thermal Shutdown Protection
S < 1µA Shutdown Current
S 20-Bump, 0.4mm Pitch 2.1mm x 1.73mm WLP
EVALUATION KIT AVAILABLE
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
2Maxim Integrated
TABLE OF CONTENTS
General Description ............................................................................ 1
Applications .................................................................................. 1
Benefits and Features .......................................................................... 1
Absolute Maximum Ratings ...................................................................... 6
Package Thermal Characteristics.................................................................. 6
Electrical Characteristics ........................................................................ 6
Typical Operating Characteristics ................................................................ 13
Bump Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Bump Description............................................................................. 27
Detailed Description........................................................................... 30
Modes of Operation .........................................................................30
Shutdown Mode ..........................................................................30
Standby Mode ...........................................................................30
Active Mode .............................................................................30
Torch Mode .............................................................................30
Flash Mode .............................................................................30
Adaptive Output Voltage Regulation.............................................................31
Current Regulator Voltage Headroom............................................................31
Step-Up Converter ..........................................................................31
Dual-Phase Operation........................................................................31
Skip Mode .................................................................................31
Current Sharing .............................................................................32
Switching Frequency Selection .................................................................32
Overvoltage Protection .......................................................................32
True Shutdown..............................................................................32
Soft-Start ..................................................................................32
End of Trigger Event .........................................................................35
Gain Selection ..............................................................................35
Low-Side Current Limit .......................................................................35
Current Regulator LED .......................................................................35
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
3Maxim Integrated
TABLE OF CONTENTS (CONTINUED)
DAC and PWM Dimming......................................................................36
DAC Control .............................................................................36
PWM Control ............................................................................36
DAC and PWM Control ....................................................................36
Ramp Control ..............................................................................37
Torch and Flash Safety Timer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
MAXFLASH Function ........................................................................39
TX_MASK .................................................................................39
NTC Control................................................................................40
Short and Open LED Detection ................................................................41
Thermal Shutdown ..........................................................................41
I2C Serial Interface ..........................................................................41
I2C Slave Address ........................................................................42
I2C Bit Transfer...........................................................................42
START and STOP Conditions................................................................42
Acknowledge ............................................................................42
Write Operations..........................................................................43
Read Operations .........................................................................44
Applications Information........................................................................ 69
Programming the I2C registers .................................................................69
Output Voltage Operating Range ...............................................................70
Inductor Selection ...........................................................................74
Input Capacitor Selection .....................................................................76
Output Capacitor Selection....................................................................76
PCB Layout ................................................................................77
Chip Information .............................................................................. 77
Simplified Block Diagram ....................................................................... 79
Ordering Information .......................................................................... 79
Package Information........................................................................... 79
Revision History .............................................................................. 80
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
4Maxim Integrated
LIST OF FIGURES
Figure 1. Detailed Block Diagram and Typical Application Circuit ....................................... 29
Figure 2. Modes of Operation ...................................................................30
Figure 3. DC-DC Converter Soft-Start for DCDC_MODE = 00 .......................................... 33
Figure 4. DC-DC Converter Soft-Start for DCDC_MODE = 01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Figure 5 DC-DC Converter Soft-Start for DCDC_MODE = 10........................................... 34
Figure 6. DC-DC Converter Soft-Start for DCDC_MODE = 11 .......................................... 34
Figure 7. Driving Two LED Configuration ........................................................... 36
Figure 8. Driving a Single LED Configuration........................................................ 36
Figure 9. Maximum Flash Timer Mode/Disabled Torch Timer Mode ...................................... 38
Figure 10. One-Shot Torch/Flash Timer Mode....................................................... 38
Figure 11. TX1_MASK or TX2_MASK During Flash Mode.............................................. 40
Figure 12. TX1_MASK and TX2_MASK Occurring at Same Time ........................................ 40
Figure 13. 2-Wire Serial Interface Timing Detail...................................................... 41
Figure 14. Bit Transfer ......................................................................... 42
Figure 15. START and STOP Conditions ........................................................... 42
Figure 16. Acknowledge........................................................................ 42
Figure 17. Write to the IC ....................................................................... 43
Figure 18. Read from the IC..................................................................... 44
Figure 19. Output Capacitor Star Connection ....................................................... 76
Figure 20. 20-Bump WLP Recommended Layout for 2x1.5A Input Current Limit............................ 78
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
5Maxim Integrated
LIST OF TABLES
Table 1. I2C Register Map ......................................................................45
Table 2. CHIP_ID1 ............................................................................ 46
Table 3. CHIP_ID2 ............................................................................ 46
Table 4. STATUS1 ............................................................................. 47
Table 5. STATUS2............................................................................. 48
Table 6. IFLASH1 ............................................................................. 49
Table 7. IFLASH2 ............................................................................. 50
Table 8. ITORCH1 ............................................................................ 51
Table 9. ITORCH2 ............................................................................ 52
Table 10. MODE_SEL.......................................................................... 53
Table 11. TX1_MASK .......................................................................... 54
Table 12. TX2_MASK .......................................................................... 55
Table 13. FLASH_RAMP_SEL ................................................................... 56
Table 14. TORCH_RAMP_SEL ................................................................... 57
Table 15. FLASH_TMR_CNTL ................................................................... 58
Table 16. TORCH_TMR_CNTL................................................................... 59
Table 17. MAXFLASH1 ......................................................................... 60
Table 18. MAXFLASH2......................................................................... 61
Table 19. MAXFLASH3......................................................................... 62
Table 20. MAXFLASH4 ........................................................................ 62
Table 21. NTC................................................................................ 63
Table 22. DCDC_CNTL1 ....................................................................... 64
Table 23. DCDC_CNTL2 ....................................................................... 65
Table 24. DCDC_LIM .......................................................................... 66
Table 25. DCDC_OUT ......................................................................... 67
Table 26. DCDC_OUT_MAX .................................................................... 68
Table 27. Maximum Output Voltage for 2A Output Current as a Function of VIN and IPEAK ..................71
Table 28. Maximum Output Voltage for 1.5A Output Current as a Function of VINand IPEAK .................72
Table 29. Maximum Output Voltage for 1.0A Output Current as a Function of VIN and IPEAK.................73
Table 30. Suggested Inductors .................................................................. 74
Table 31. Suggested Input Capacitors............................................................. 76
Table 32. Suggested Output Capacitors ........................................................... 77
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
6Maxim Integrated
ABSOLUTE MAXIMUM RATINGS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
PACKAGE THERMAL CHARACTERISTICS (Note 2)
ELECTRICAL CHARACTERISTICS
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
Note 2: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Note 1: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device
can be exposed to during board level solder attach and rework. This limit permits only the use of the solder profiles recom-
mended in the industry-standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow.
Preheating is required. Hand or wave soldering is not allowed.
VDD, IN, REG_IN to AGND ...................................-0.3V to +6.0V
OUT_A, OUT_B to PGND_A, PGND_B ................-0.3V to +6.0V
LX_A to PGND_A .......................................-0.3V to VOUT + 0.3V
LX_B to PGND_B .......................................-0.3V to VOUT + 0.3V
FLED1, FLED2 to AGND .......................-0.3V to VREG_IN + 0.3v
TX1_MASK, TX2_MASK, TORCH_EN,
NTC to AGND ........................................... -0.3V to VIN + 0.3V
SDA, SCL, FLASH_STB to AGND ................ -0.3V to VIN + 0.3V
AGND to PGND_A, PGND_B ...............................-0.3V to +0.3V
ILX_A, ILX_B Current (rms) per Phase ................................2.0A
Continuous Power Dissipation (TA = +70NC)
(derate 21.7mW/NC above +70NC) ............................1736mW
Operating Temperature ...................................... -40NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range ............................ -65NC to +150NC
Soldering Temperature (reflow) (Note 1) ........................+260NC
WLP
Junction to Ambient Thermal Resistance (qJA) ..........46°C/W
PARAMETER CONDITIONS MIN TYP MAX UNITS
GENERAL
IN Operating Voltage Range 2.5 5.5 V
VDD Operating Voltage Range 1.62 3.6 V
IN Undervoltage Lockout
(IN_UVLO) Threshold VIN falling, 60mV (typ) hysteresis 2.10 2.20 2.30 V
VDD Under voltage Lockout
(VDD_UVLO) Threshold VDD falling 0.65 0.9 1.0 V
IN Shutdown Supply Current VIN = 5.5V, VDD = 0V TA = +25NC0.01 1 FA
TA = +85NC0.1
VDD Standby Supply Current VIN = 5.5V, VDD = VSDA = VSCL =
3.6V, DCDC_MODE = 00
TA = +25NC0.01 1 FA
TA = +85NC0.1
IN Standby Supply Current
VIN = 5.5V,
VDD = VSCL = VSDA = 3.6V,
DCDC_MODE = 00,
DC-DC converter and current
regulators are off
TA = -40NC to +85NC1.5 5 FA
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
7Maxim Integrated
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
LOGIC INTERFACE
Logic Input High Voltage
VDD = 1.62V to 3.6V SDA, SCL,
FLASH_STB
0.7 x
VDD
VDD +
0.3V V
VIN = 2.5V to 5.5V
TORCH_EN,
TX1_MASK,
TX2_MASK
1.25 VIN +
0.3V V
Logic Input Low Voltage
VDD = 1.62V to 3.6V SDA, SCL,
FLASH_STB 0.4
V
VIN = 2.5V to 5.5V
TORCH_EN,
TX1_MASK,
TX2_MASK
0.4
Pulldown Resistor
VDD = 1.62V to 3.6V
FLASH_STB_PD = 1 FLASH_STB 400 800 1600
kI
VIN = 2.5V to 5.5V
TORCH_EN_PD = 1,
TX1_MASK_PD = 1,
TX2_MASK_PD = 1
TORCH_EN,
TX1_MASK,
TX2_MASK
400 800 1600
Logic Input Current
VDD = 1.62V to 3.6V,
FLASH_STB_PD = 0
TA = +25NC-1 0.01 +1
FA
TA = +85NC0.1
VIN = 2.5V to 5.5V
TORCH_EN_PD = 0,
TX1_MASK_PD = 0,
TX2_MASK_PD = 0
TA = +25NC-1 0.01 +1
TA = +85NC0.1
LOGIC INTERFACE TIMING
FLASH_STB Enable Delay in
Active Mode (tFLASH_EN_ACTIV)
See Figure 4, from FLASH_STB rising edge until start of
current regulator ramp up (Note 4) 5Fs
TORCH_EN Enable Delay in
Active Mode (tTORCH_EN_ACTIV)
See Figure 4, from TORCH_EN rising edge until start of
current regulator ramp up (Note 4) 5Fs
FLASH_STB Enable Delay in
Standby Mode
(tFLASH_STB_STDBY)
See Figure 3, from FLASH_STB rising edge until start of
precharge of the output (Note 4) 30 Fs
TORCH_EN Enable Delay in
Standby Mode
(tTORCH_EN_STDBY)
See Figure 3, from TORCH_EN rising edge until start of
precharge of the output (Note 4) 30 Fs
Precharging of Output
(tOUT_PCHG)
See Figures 3–6, VIN = 3.6, COUT = 10FF, charging the
output from 0V until LX starts switching (Note 4) 600 Fs
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
8Maxim Integrated
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Soft-Start Time Duration,
(tDCDC_SS)See Figures 3, 4, and 5 (Note 4) DCDC_SS
x 8 Fs
TX_MASK Trigger to Reduced
Output Current (tTX_MASK_EN)
See Figures 9 and 10
From TX1_MASK, TX2_MASK triggered until output
current is at reduced output current (Note 4)
7Fs
Standby to Active Mode
(tSTDBY2ACTIV)
See Figures 5 and 6
Time to transition from standby to active mode (Note 4) 25 Fs
I2C INTERFACE (Note 4)
SDA Output Low Voltage ISDA = 3mA 0.03 0.4 V
I2C Clock Frequency 400 kHz
Bus-Free Time Between START
and STOP tBUF 1.3 Fs
Hold Time Repeated START
Condition tHD_STA 0.6 0.1 Fs
SCL Low Period tLOW 1.3 0.2 Fs
SCL High Period tHIGH 0.6 0.2 Fs
Setup Time Repeated START
Condition tSU_STA 0.6 0.1 Fs
SDA Hold Time tHD_DAT 0 -0.01 Fs
SDA Setup Time tSU_DAT 100 50 ns
Setup Time for STOP Condition tSU_STO 0.6 0.1 Fs
STEP-UP DC-DC CONVERTER
OUT Voltage Range Adaptive controlled 2.3 5.2 V
Output Adaptive Regulation
Step Size
Smallest step size when output voltage is in adaptive
regulation VADPT_REG_STEP 6.25 mV
Digital Overvoltage Protection
(OVP_D)
When operating in
adaptive mode
OVP_TH = 00 0x140h (4.3V)
9-bit
digital
code
OVP_TH = 01 0x170h (4.6V)
OVP_TH = 10 0x1A0h (4.9V)
OVP_TH = 11 0x1D0h (5.2V)
Analog Overvoltage Protection
OVP_TH = 00 4.35 4.5 4.65
V
OVP_TH = 01 4.65 4.8 4.95
OVP_TH = 10 4.95 5.1 5.25
OVP_TH = 11 5.25 5.4 5.55
Output Threshold for Minimum
Duty Cycle to Bypass Mode
VOUT_MIND
Output voltage where the DC-DC converter goes from
operating at minimum duty cycle to dropout operation,
during a disabling of the DC-DC converter,
DCDC_MODE = 00
VIN +
200mV V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
9Maxim Integrated
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output Threshold for Dropout
Operation to OFF Mode
VOUT_OFF
Output voltage where the DC-DC converter goes from
operating in dropout mode to true shutdown, during a
disabling of the DC-DC converter, DCDC_MODE = 00
VIN +
150mV V
Charge Mode Comparator
Threshold
Output voltage where the DC-DC converter goes from
operating at minimum duty cycle to soft start.
VIN -
300mV V
Adaptive Output Step Time
Time between sampling of adaptive regulation during
soft-start (Note 5) 1Fs
Time between sampling of adaptive regulation (Note 5) 8
IN Supply Current
VOUT = 4.5V, IOUT = 0mA, switching 4MHz PWM mode
dual-phase operation (Note 2) 14
mA
VOUT = 4.5V, IOUT = 0mA, switching 2MHz PWM mode
dual-phase operation (Note 2) 15
VOUT = 4.5V, IOUT = 0mA, no switching (skip mode) 450 FA
Low-Side Current Limit
(Static Limits)
(Phases A and B)
DCDC_ILIM = 00 1.11 1.25 1.37
A
DCDC_ILIM = 01 1.35 1.5 1.65
DCDC_ILIM = 10 1.57 1.75 1.93
DCDC_ILIM = 11 1.80 2.0 2.20
Current Sharing Delta current between phase A and phase B (Note 4),
excluding external components 0 %
Phase A Zero-Crossing Threshold
(Static, Phases A and B) 120 mA
LX_ High-Side On-Resistance
(Phases A and B) LX_ to OUT_, ILX_ = -200mA, VOUT = 3.6V 130 185 mI
LX_ Low-Side On-Resistance
(Phases A and B) LX_ to PGND_, ILX_ = 200mA, VOUT = 3.6V 100 160 mI
Load Regulation
VIN = 3.4V, VOUT = 4.5V, enhanced mode
(DCDC_GAIN = 1) (for adaptive mode only) (Note 4) 50 mV/A
VIN = 3.4V, VOUT = 4.5V, enhanced mode
(DCDC_GAIN = 1) (for program mode only) (Note 4) 100 mV/A
LX_ Leakage
(Phase A, Phase B) VLX_ = 5.5V TA = +25NC0.1 2 FA
TA = +85NC0.1
Operating Frequency
(Phase A, Phase B) DCDC_OPERATION[2:0] = 010 TA = -40NC to +85NC3.90 4.0 4.10 MHz
Maximum Duty Cycle
(Phase A, Phase B) DCDC_OPERATION[2:0] = 011 70 %
Minimum Duty Cycle During non-skip mode (DCDC_OPERATION[2:0] = 011) 3.3 %
During skip mode (Note 4) 0 %
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
10Maxim Integrated
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
LED CURRENT SOURCE DRIVERS
REG_IN Supply Current
(FLED1, FLED2)
FLED_ enabled in torch mode with PWM dimming set
to maximum current setting, supply current measured
during off period of PWM cycle
100 FA
IN Supply Current
(FLED1, FLED2)
FLED_ enabled in torch mode with PWM dimming set
to maximum current setting, supply current measured
during off period of PWM cycle
25 FA
LED Current Setting Range
(FLED1, FLED2)
FLED_ enabled in flash mode,
current range in 15.625mA steps 15.625 1000
mA
FLED_ enabled in torch mode, with DAC mode active,
current range in 3.91mA steps 3.91 250
FLED_ enabled in torch mode with PWM dimming active,
current range in 125mA steps 125.0 1000
PWM Dimming Duty Cycle Setting
Range
FLED_ enabled in torch mode with PWM dimming active,
duty cycle range in 3.125% steps (Note 5) 3.125 25 %
PWM Dimming Frequency Setting
Range
FREQ_PWM[1:0] = 00 (Note 5) 7.8
kHz
FREQ_PWM[1:0] = 01 (Note 5) 1.9
FREQ_PWM[1:0] = 10 (Note 5) 0.488
FREQ_PWM[1:0] = 11 (Note 5) 0.122
LED Peak Current Overshoot
FLED_ enabled in torch mode with PWM dimming set
to maximum current setting, maximum LED current
overshoot during initial ramping up (Note 4)
10 %
LED Current Settling Time
FLED_ enabled in torch mode with PWM dimming set to
maximum current setting. Time for LED current to settle
to less than 10% from nominal setting (not including
ramp time) (Note 4)
6Fs
LED Current Accuracy Flash
Mode or Torch Mode with PWM
Dimming (FLED1, FLED2)
625mA to 1000mA -5 +5
%
218.75mA to 609.375mA -7 +7
62.5mA to 203.125mA -10 +10
31.25mA to 46.875mA -12 +12
15.625mA -14 +14
LED Current Accuracy
Torch Mode
(FLED1, FLED2)
156.25 to 250mA -5 +5
%
54.6875mA to 152.34375mA -7 +7
15.625mA to 50.78125mA -10 +10
7.8125mA to 11.71875mA -12 +12
3.91mA -14 +14
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
11Maxim Integrated
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
LED Current Dropout Voltage
Flash Mode or Torch Mode with
PWM Dimming (FLED1, FLED2)
1000mA setting at -10% 80
mV
1000mA setting at -1% (Note 4) 100
LED Current Dropout Voltage
Torch Mode (FLED1, FLED2)
250mA setting at -10% 80 mV
250mA setting at -1% (Note 4) 100
LED Adaptive Mode Threshold
Voltage Setting Range
(FLED1, FLED2)
FLED_ enabled in flash
mode or torch mode
DCDC_ADPT_REG = 00 120
mV
DCDC_ADPT_REG = 01 150
DCDC_ADPT_REG = 10 180
DCDC_ADPT_REG = 11 210
LED Leakage Current REG_IN = 5.5V,
FLED_ = 0V
TA = +25NC0.1 2 FA
TA = +85NC1
REG_IN UVLO Voltage Minimum voltage on REG_IN required before FLED_
current regulators are enabled 2.2 2.3 2.4 V
TIMERS
Flash Duration Timer Range
In 0.256ms steps (Note 5) 0.128 0.896
ms
In 0.512ms steps (Note 5) 0.896 2.944
In 1.024ms steps (Note 5) 2.944 11.136
In 2.048ms steps (Note 5) 11.136 43.904
In 4.096ms steps (Note 5) 43.904 437.12
In 8.192ms steps (Note 5) 437.12 699.264
Torch Duration Timer Range
TORCH_TMR0
In 131.072ms steps (Note 5) 122.88 561.1
ms
In 262.144ms steps (Note 5) 561.1 1564.67
In 524.288ms steps (Note 5) 1564.67 5767.17
In 1048.576ms steps (Note 5) 5767.17 22536.19
Torch and Flash Duration Timer
Accuracy
TA = 0NC to +85NC (Note 4) -2.5 0 +2.5 ms
TA = -40NC to +85NC (Note 4) -3 0 +3
Flash Mode Ramp Rate Settings
LED current ramp-
up time (Note 5)
Time it takes for current regulator to
ramp from 0mA to full scale current 384 32896 Fs
LED current ramp-
down time. (Note 5)
Time it takes for current regulator to
ramp from full scale current to 0mA 384 32896 Fs
Torch Mode Ramp Rate Settings
LED current ramp-
up time (Note 5)
Time it takes for current regulator to
ramp from 0mA to full scale current 16.392 2097 ms
LED current ramp-
down time (Note 5)
Time it takes for current regulator to
ramp from full scale current to 0mA 16.392 2097 ms
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
12Maxim Integrated
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
PARAMETER CONDITIONS MIN TYP MAX UNITS
DIE PROTECTION
Shorted LED detection Threshold
FLED1, FLED2 1 V
Short Debounce timer
FLED1, FLED2
From LED short detected until LED current regulator is
disabled (Note 5) 1.024 ms
OVP_A Debounce Timer Time where adaptive regulation threshold is set at OVP_A
threshold until current regulator is disabled (Note 5) 1.024 ms
OVP_D Debounce Timer
Time where adaptive regulation threshold is set at
OVP_D threshold until current regulator is disabled
(Note 5)
384 Fs
IN_UVLO/THERM Debounce
Timer
Either time where VIN is less than IN_UVLO threshold or
thermal threshold is exceeded until the current regulator
is disabled (Note 5)
0.512 ms
Thermal Shutdown Hysteresis (Note 4) 20 NC
Thermal Shutdown TJ = rising (Note 4) +160 NC
NTC THERMAL PROTECTION
NTC Bias NTC_BIAS_25C
TA = +25NC194 200 206 FA
NTC Bias Temperature
Coefficient NTC_T_COMP (Note 4) 0.020 FA/NC
NTC Bias On-Time
(tNTC_TORCH_ON)
Time NTC bias is enabled before temperature
measurement is performed in torch mode (Note 5) 0.512 ms
NTC Bias On Interval
(NTC_TORCH_OFF)
Time between enabling of NTC bias in torch mode
(Note 5) 131 ms
NTC Over Temperature Detection
Threshold Range In 50mV steps, NTC falling 200 550 mV
NTC Over Temperature Threshold
Hysteresis 50 mV
NTC Over Temperature Threshold
Accuracy For NTC_TH at the 200mV setting -2 +2 %
NTC Short Detection Threshold 55 70 120 mV
MAXFLASH
Low Battery Detect Threshold
Range In 33mV steps, VIN falling 2.4 3.4 V
Low Battery Voltage Threshold
Accuracy ±2.5 %
Low Battery Voltage Hysteresis
Programmable Range In 50mV steps 50 350 mV
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
13Maxim Integrated
Typical Operating Characteristics
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 3.6V, VDD = 1.8V, VPGND_A = VPGND_B = VAGND = 0V, VTX1_MASK = VTX2_MASK = VTORCH_EN = VFLASH_STB = 0V,
fSW = 4MHz, TA = -40NC to +85NC, unless otherwise noted. Typical values are at TA = +25NC. See Figure 1.) (Note 3)
Note 3: All devices are 100% production tested at TA = +25NC. Limits over the operating temperature range are guaranteed by
design.
Note 4: Parameter not production tested. Parameter guaranteed by design through characterization.
Note 5: Parameter production tested through scan. Parameter guaranteed by design through characterization.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Low Battery Inhibit Timer Falling in 256Fs steps (Note 5) 256 2048 Fs
Rising in 256Fs steps (Note 5) 256 2048
Low Battery Inhibit Time
Accuracy (Note 4) -3 +3 %
DC-DC CONVERTER EFFICIENCY vs.
LOAD CURRENT (VIN = 2.5V, VOUT = 4V) 1µH
MAX77387 toc01
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
2MHz FREQUENCY
SCALING AND SKIP
4MHz FREQUENCY
SCALING AND SKIP
1MHz SKIP
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VIN = 2.5V, VOUT = 4V, FPWM)
MAX77387 toc02
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
1MHz, 1µH
4MHz, 0.47µH
2MHz, 1µH
DC-DC CONVERTER EFFICIENCY vs.
LOAD CURRENT (VIN = 2.5V, VOUT = 4V) 1µH
MAX77387 toc03
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
2MHz FREQUENCY
SCALING FPWM
4MHz FREQUENCY
SCALING FPWM
DC-DC CONVERTER EFFICIENCY vs.
LOAD CURRENT (VIN = 3.2V, VOUT = 4V) 1µH
MAX77387 toc04
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
4MHz FREQUENCY
SCALING SKIP
2MHz FREQUENCY
SCALING SKIP
1MHz SKIP
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VIN = 3.2V, VOUT = 4V, FPWM)
MAX77387 toc05
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
2MHz, 1µH
1MHz, 1µH
4MHz, 0.47µH
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VIN = 3.2V, VOUT = 4V) 1µH
MAX77387 toc06
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
4MHz FREQUENCY
SCALING FPWM
2MHz FREQUENCY
SCALING FPWM
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
14Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
DC-DC CONVERTER EFFICIENCY
vs. LOAD CURRENT, VOUT = 4.5V 4MHz
FREQUENCY SCALING AND SKIP 1µH
MAX77387 toc10
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY
vs. LOAD CURRENT, VOUT = 4.5V 2MHz
FREQUENCY SCALING AND SKIP 1µH
MAX77387 toc11
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VOUT = 4V, 4MHz FPWM, 0.47µH)
MAX77387 toc12
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VIN = 3.7V, VOUT = 4V) 1µH
MAX77387 toc07
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
2MHz FREQUENCY
SCALING SKIP
4MHz FREQUENCY
SCALING SKIP
1MHz SKIP
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VIN = 3.7V, VOUT = 4V, FPWM)
MAX77387 toc08
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
4MHz, 0.47µH
2MHz, 1µH
1MHz, 1µH
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VIN = 3.7V, VOUT = 4V) 1µH
MAX77387 toc09
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
4MHz FREQUENCY
SCALING FPWM
2MHz FREQUENCY
SCALING FPWM
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
15Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT, VOUT = 4.5V 2MHz FPWM 1µH
MAX77387 toc13
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY
vs. LOAD CURRRENT, VOUT = 5V 4MHz
FREQUENCY SCALING AND SKIP 1µH
MAX77387 toc14
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY
vs. LOAD CURRRENT, VOUT = 5V 2MHz
FREQUENCY SCALING AND SKIP 1µH
MAX77387 toc15
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.10.01
10
20
30
40
50
60
70
80
90
100
0
0.001 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT (VOUT = 5V, 4MHz FPWM, 0.47µH)
MAX77387 toc16
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
VIN = 2.5V
VIN = 3.2V VIN = 3.7V
DC-DC CONVERTER EFFICIENCY vs. LOAD
CURRENT, VOUT = 5V 2MHz FPWM 1µH
MAX77387 toc17
OUTPUT CURRENT (A)
EFFICIENCY (%)
10.1
10
20
30
40
50
60
70
80
90
100
0
0.01 10
VIN = 2.5V
VIN = 3.2V
VIN = 3.7V
DC-DC CONVERTER EFFICIENCY
vs. VIN, VOUT = 4.5V, 4MHz
FREQUENCY SCALING AND SKIP 1µH
MAX77387 toc18
INPUT VOLTAGE (V)
EFFICIENCY (%)
4.03.0 3.5
10
20
30
40
50
60
70
80
90
100
0
2.5 4.5
IOUT = 1A
= 100mA
= 2A
= 10mA
= 1mA
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
16Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
DC-DC CONVERTER EFFICIENCY vs. VIN,
2MHz FREQUENCY SCALING AND SKIP 1µH
MAX77387 toc19
INPUT VOLTAGE (V)
EFFICIENCY (%)
4.03.0 3.5
10
20
30
40
50
60
70
80
90
100
0
2.5 4.5
IOUT = 1A
= 100mA
= 2A
= 10mA
= 1mA
VOUT = 4.5V
LED EFFICIENCY vs. LED CURRENT (4MHz,
FREQUENCY SCALING, SKIP ALLOWED)
MAX77387 toc20
LED CURRENT (A)
EFFICIENCY (%)
600 800200 400
10
20
30
40
50
60
70
80
90
100
0
0 1000
2 LEDS, VF = 3V
VIN = 4.2V
VIN = 3.6V
VIN = 2.5V
LED EFFICIENCY vs. LED CURRENT (2MHz,
FREQUENCY SCALING, SKIP ALLOWED)
MAX77387 toc21
LED CURRENT (A)
EFFICIENCY (%)
600 800200 400
10
20
30
40
50
60
70
80
90
100
0
0 1000
2 LEDS, VF = 3V
VIN = 4.2V
VIN = 3.6V
VIN = 2.5V
LED EFFICIENCY vs. LED CURRENT
(4MHz, FPWM)
MAX77387 toc22
LED CURRENT (A)
EFFICIENCY (%)
600 800200 400
10
20
30
40
50
60
70
80
90
100
0
0 1000
2 LEDS, VF = 3V
VIN = 4.2V
VIN = 3.6V
VIN = 2.5V
LED EFFICIENCY vs. LED CURRENT
(2MHz, FPWM)
MAX77387 toc23
LED CURRENT (A)
EFFICIENCY (%)
600 800200 400
10
20
30
40
50
60
70
80
90
100
0
0 1000
2 LEDS, VF = 3V
VIN = 4.2V
VIN = 3.6V
VIN = 2.5V
INPUT CURRENT LIMIT
vs. TEMPERATURE
MAX77387 toc24
TEMPERATURE (°C)
INPUT CURRENT LIMIT (A)
7550250-25
1.2
1.4
1.6
1.8
2.0
2.2
1.0
-50 100
ILIM = 2A
ILIM = 1.75A
ILIM = 1.5A
ILIM = 1.25A
VIN = 3.2V
VOUT = 4.5V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
17Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
SWITCHING FREQUENCY
vs. TEMPERATURE (4MHz FPWM)
MAX77387 toc25
TEMPERATURE (°C)
SWITCHING FREQUENCY (MHz)
7550-25 0 25
3.85
3.90
3.95
4.00
4.05
4.10
4.15
4.20
3.80
-50 100
VIN = 2.5V
VIN = 4.2V
VIN = 3.7V
VIN = 3.4V
VIN = 3.1V
OUTPUT VOLTAGE ACCURACY vs. LOAD
CURRENT (VIN = 3.6V VOUT = 5V FPWM)
MAX77387 toc28
LOAD CURRENT (mA)
OUTPUT VOLTAGE ACCURACY (%)
15001000500
-8
-7
-6
-5
-4
-3
-2
-1
0
1
-9
0 2000
DCDC_GAIN = 0
2MHz
1MHz
4MHz
SWITCHING FREQUENCY
vs. TEMPERATURE (2MHz FPWM)
MAX77387 toc26
SWITCHING FREQUENCY (MHz)
1.92
1.94
1.96
1.98
2.00
2.02
2.04
2.06
2.08
2.10
1.90
TEMPERATURE (°C)
7550-25 025-50 100
VIN = 2.5V
VIN = 4.2V
VIN = 3.7V
VIN = 3.4V
VIN = 3.1V
OUTPUT VOLTAGE ACCURACY vs. LOAD
CURRENT (VIN = 3.6V, VOUT = 5V FPWM)
MAX77387 toc29a
LOAD CURRENT (mA)
OUTPUT VOLTAGE ACCURACY (%)
15001000500
-7
-6
-5
-4
-3
-2
-1
0
-8
0 2000
4MHz
2MHz
1MHz
DCDC_GAIN = 1
SWITCHING FREQUENCY
vs. TEMPERATURE (1MHz FPWM)
MAX77387 toc27
SWITCHING FREQUENCY (MHz)
0.960
0.970
0.980
0.990
1.000
1.010
1.020
1.030
1.040
1.050
0.950
TEMPERATURE (°C)
7550-25 025-50 100
VIN = 2.5V
VIN = 4.2V
VIN = 3.7V
VIN = 3.4V
VIN = 3.1V
OUTPUT VOLTAGE ACCURACY vs. LOAD
CURRENT (VIN = 3.6V, VOUT = 5V FPWM)
MAX77387 toc29b
LOAD CURRENT (mA)
OUTPUT VOLTAGE ACCURACY (%)
150010005000 2000
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
-10
DCDC_GAIN = 1
2MHz
4MHz
1MHz
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
18Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
OUTPUT VOLTAGE ACCURACY
vs. TEMPERATURE
MAX77387 toc30
TEMPERATURE (°C)
-50 100
OUTPUT VOLTAGE ACCURACY (%)
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
-0.5
75
50250-25
VIN = 3.6V
VIN = 5V
SOFT-START (4MHz, FPWM)
MAX77387 toc31
200mA/div
VIN = 2.5V
VOUT = 4.5V
400µs/div
2V/div
1A/div
0
0
0
VOUT
IIN
ILED1
SOFT-START (4MHz, FREQUENCY
SCALING, SKIP ALLOWED)
MAX77387 toc32
200mA/div
VIN = 3.4V
VOUT = 4.5V
400µs/div
2V/div
1A/div
0
0
0
VOUT
IIN
ILED1
LINE TRANSIENT (2MHz, FPWM)
MAX77387 toc34
500mA/div
500mA/div
200mV/div
AC-COUPLED
IOUT = 500mA
200µs/div
3.6V/div
3.1V/div
0
0
VOUT
VIN
ILXA
ILXB
LINE TRANSIENT (4MHz, FPWM)
MAX77387 toc33
500mA/div
500mA/div
100mV/div
AC-COUPLED
IOUT = 500mA
200µs/div
3.6V/div
3.1V/div
0
0
VOUT
VIN
ILXA
ILXB
LOAD TRANSIENT (500mA-1A-500mA) 4MHz,
FREQUENCY SCALING, SKIP ALLOWED
MAX77387 toc35
1A/div
2V/div
500mV/div
AC-COUPLED
VIN = 3.6V
VOUT = 5V
STANDARD GAIN
20µs/div
1A
500mA
0
0
IOUT
VOUT
VIN
ILXA
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
19Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
LOAD TRANSIENT (0A-1A-0A) 4MHz,
FREQUENCY SCALING, SKIP ALLOWED
MAX77387 toc36
1A/div
2V/div
500mV/div
AC-COUPLED
VIN = 3.6V
VOUT = 5V
DCDC_GAIN = 0
20µs/div
1A
0A
0
IOUT
VOUT
VIN
ILXA
LOAD TRANSIENT (500mA-1A-500mA)
2MHz FPWM
MAX77387 toc37
1A/div
2A/div
500mA/div
AC-COUPLED
VIN = 3.6V
VOUT = 5V
DCDC_GAIN = 0
20µs/div
1A
500mA
0
0
IOUT
VOUT
VIN
ILXA
LOAD TRANSIENT (1mA-1A-1mA)
2MHz FPWM
MAX77387 toc38
1A/div
2V/div
500mV/div
AC-COUPLED
VIN = 3.6V
VOUT = 5V
DCDC_GAIN = 0
20µs/div
1A
0mA
0
IOUT
VOUT
VIN
ILXA
LOAD TRANSIENT (1mA-2A-1mA)
4MHz FPWM
MAX77387 toc40
200µs/div
1V/div
AC-COUPLED
2A
0A
2V/div
2A/div
0
0V
IOUT
VOUT
ILXA
VIN
ILIM IS CONSTANTLY BEING TRIPPED
DCDC_GAIN = 0
LOAD TRANSIENT (1mA-2A-1mA)
2MHz FPWM
MAX77387 toc39
ILIM IS CONSTANTLY BEING TRIPPED
DCDC_GAIN = 0
200µs/div
1V/div
AC-COUPLED
2A
0A
2V/div
2A/div
0V
0V
IOUT
VOUT
ILXA
VIN
LOAD TRANSIENT (1mA-2A-1mA)
2MHz FPWM
MAX77387 toc41
2A/div
2V/div
1A/div
AC-COUPLED
VIN = 3.6V
VOUT = 5V
DCDC_GAIN = 1
20µs/div
2A
0A
0
0
IOUT
VOUT
VIN
ILXA
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
20Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
MAX77387 toc42
100mA/div
2V/div
10mV/div
AC-COUPLED
IOUT = 30mA, VOUT = 4.5V, VIN = 3.4V
200ns/div
0A
0V
VOUT
ILXB
VLXA
ILXA
LIGHT-LOAD SWITCHING
WAVEFORMS (4MHz FPWM)
MAX77387 toc43
2V/div
200mA /div
20mV/div
AC-COUPLED
IOUT = 30mA, VOUT = 4.5V, VIN = 3.4V
400ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
LIGHT-LOAD SWITCHING WAVEFORMS
(2MHz FPWM)
LIGHT-LOAD SWITCHING WAVEFORMS (4MHz,
FREQUENCY SCALING, SKIP ALLOWED)
MAX77387 toc44
100mA/div
10mV/div
AC-COUPLED
IOUT = 30mA, VOUT = 4.5V, VIN = 3.4V
400ns/div
0A
0
VOUT
VLXA
ILXA
ILXB
MAX77387 toc46
500mA/div
2V/div
20mV/div
AC-COUPLED
IOUT = 300mA, VOUT = 4.5V, VIN = 3.4V
400ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
MODERATE-LOAD SWITCHING
WAVEFORMS (2MHz,FPWM)
MAX77387 toc45
200mA/div
2V/div
20mV/div
AC-COUPLED
IOUT = 300mA, VOUT = 4.5V, VIN = 3.4V
200ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
MODERATE-LOAD SWITCHING
WAVEFORMS (4MHz,FPWM)
MAX77387 toc47
500mA/div
2V/div
20mV/div
AC-COUPLED
IOUT = 1000mA, VOUT = 4.5V, VIN = 3.4V
200ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
HEAVY-LOAD SWITCHING
WAVEFORMS (4MHz,FPWM)
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
21Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
MAX77387 toc48
500mA/div
2V/div
20mV/div
AC-COUPLED
IOUT = 1000mA, VOUT = 4.5V, VIN = 3.4V
400ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
HEAVY-LOAD SWITCHING
WAVEFORMS (2MHz,FPWM)
MAX77387 toc49
500mA/div
2V/div
20mV/div
AC-COUPLED
VIN = 2.5V, VOUT = 4.5V
200ns/div
0V
0A
VOUT
VLXA
ILXA
ILXB
1.25A CURRENT LIMIT
MAX77387 toc50
500mA/div
2V/div
20mV/div
AC-COUPLED
VIN = 3V, VOUT = 5V
200ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
1.5A CURRENT LIMIT
MAX77387 toc52
500mA/div
2V/div
20mV/div
AC-COUPLED
VIN = 3V, VOUT = 5V
200ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
2A CURRENT LIMIT
MAX77387 toc51
500mA/div
2V/div
20mV/div
AC-COUPLED
200ns/div
0A
0V
VOUT
VLXA
ILXA
ILXB
VIN = 3V, VOUT = 5V
1.75A CURRENT LIMIT
LED CURRENT RIPPLE (4MHz, FWPM)
MAX77387 toc53
10mA/div
10mA/div
10mV/div
AC-COUPLED
2x IFLED = 100mA
VIN = 3.6V
VOUT
IFLED1
IFLED2
4µs/div
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
22Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
LED CURRENT RIPPLE (2MHz, FWPM)
MAX77387 toc54
10mA/div
10mA/div
10mV/div
AC-COUPLED
2x IFLED = 100mA
VIN = 3.6V
VOUT
IFLED1
IFLED2
2µs/div
LED CURRENT RIPPLE (4MHz, FWPM)
MAX77387 toc55
10mA/div
10mA/div
10mV/div
AC-COUPLED
2x IFLED = 500mA
VIN = 3.6V
VOUT
IFLED1
IFLED2
2µs/div
LED CURRENT RIPPLE (2MHz, FWPM)
MAX77387 toc56
20mV/div
AC-COUPLED
10mA/div
10mA/divIFLED2
IFLED1
VOUT
2µs/div
2x IFLED = 500mA
VIN = 3.6V
LED CURRENT RIPPLE (2MHz, FWPM)
MAX77387 toc58
50mV/div
10mA/div
10mA/div
IFLED2
IFLED1
VOUT
2µs/div
2x IFLED = 1000mA
VIN = 3.6V
LED CURRENT RIPPLE (4MHz, FWPM)
MAX77387 toc57
20mV/div
AC-COUPLED
10mA/div
10mA/divIFLED2
IFLED1
VOUT
10µs/div
2x IFLED = 1000mA
VIN = 3.6V
MAX77387 toc59
2V/div
2V/div
100mA/div
0A
0V
0A
0V
100mA/div
IFLED2
VOUT
IFLED1
VTORCH_EN
2ms/div
4MHz, FPWM
2 x IFLED = 100mA (DAC MODE)
TORCH ENABLED BY TORCH_EN
(ADAPTIVE MODE NO PREBIAS)
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
23Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
MAX77387 toc60
2V/div
2V/div
100mA/div
0A
0V
0A
0V
100mA/div
IFLED2
VOUT
IFLED1
VTORCH_EN
2ms/div
4MHz, FPWM
2 x IFLED = 100mA (DAC MODE)
TORCH ENABLED BY TORCH_EN
(ADAPTIVE MODE BIASED)
TORCH ENABLED BY TORCH_EN
(ADAPTIVE MODE NO PREBIAS)
MAX77387 toc61
2V/div
2V/div
100mA/div
0A
0A
100mA/div
IFLED2
VOUT
IFLED1
VTORCH_EN
400µs/div
4MHz, FPWM
2x IFLED = 125mA
(PWM MODE. 25% DUTY CYCLE)
TORCH ENABLED BY TORCH_EN
(ADAPTIVE MODE BIASED)
MAX77387 toc62
2V/div
2V/div
100mA/div
0A
0A
100mA/div
IFLED2
VOUT
IFLED1
VTORCH_EN
400µs/div
4MHz, FPWM
2x IFLED = 125mA (PWM MODE. 25% DUTY CYCLE)
FLASH ENABLED BY FLASH_STB
(ADAPTIVE MODE BIASED)
MAX77387 toc64
2V/div
2V/div
500mA/div
0A
0A
500mA/div
IFLED2
VOUT
IFLED1
VFLASH_STB
400µs/div
4MHz, FPWM
2x IFLED = 1A
FLASH ENABLED BY FLASH_STB
(ADAPTIVE MODE NO PREBIAS)
MAX77387 toc63
2V/div
2V/div
500mA/div
0A
0A
500mA/div
IFLED2
VOUT
IFLED1
VFLASH_STB
200µs/div
4MHz, FPWM
2x IFLED = 1A
FLASH ENABLED BY FLASH_STB
(ADAPTIVE MODE BIASED)
MAX77387 toc65
500mV/div
2V/div
500mA/div
0A
0A
500mA/div
IFLED2
VOUT
IFLED1
VFLASH_STB
400µs/div
4MHz, FPWM
2x IFLED = 1A
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
24Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
FLASH RAMP DOWN
MAX77387 toc66
1V/div
500mA/div
0A
0A
0A
500mA/div
IFLED2
VOUT
IFLED1
100µs/div
4MHz, FPWM
2x IFLED = 1A
FLASH RAMP DOWN
MAX77387 toc67
2V/div
500mA/div
0A
0A
0A
500mA/div
IFLED2
VOUT
IFLED1
200µs/div
4MHz, FPWM
2x IFLED = 1A
TX1 MASK (RISING EDGE)
MAX77387 toc68
0A
500mA/div
IFLED2
VTX1_MASK
VTX2_MASK
VFLASH_STB
IFLED1
100ms/div
IFLED1 = IFLED2 = 1A
TX1 MASK = 500mA
TX2 MASK = OFF
TX1 AND TX2 MASKS
MAX77387 toc70
0A
500mA/div
IFLED2
VTX1_MASK
VTX2_MASK
VFLASH_STB
IFLED1
100ms/div
IFLED1 = IFLED2 = 1A
TX1 MASK = 0A
TX2 MASK = 500mA
TX1 AND TX2 MASKS
MAX77387 toc69
0A
500mA/div
IFLED2
VTX1_MASK
VTX2_MASK
VFLASH_STB
IFLED1
100ms/div
IFLED1 = IFLED2 = 1A
TX1 MASK = 0A
TX2 MASK = 500mA
MAXFLASH
MAX77387 toc71
200mV/div
AC-COUPLED
100mA/div
0A
0A
100mA/div
IFLED2
VOUT
IFLED1
10ms/div
350mV HYSTERESIS
3.39V THRESHOLD
1024µs INPUT TIMER
VIN = 3.55V
VOUT = 5V
IFLED1 = IFLED2 = 1A
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
25Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
LED FLASH CURRENT ACCURACY
vs. LOAD CURRENT
MAX77387 toc72
LED FLASH CURRENT SETTING (mA)
LED FLASH CURRENT ACCURACY (%)
800600400200
-2
0
2
4
6
8
-4
0 1000
ILED2
ILED1
VIN = 3.6V
FLASH CURRENT ACCURACY
vs. TEMPERATURE
MAX77387 toc73
TEMPERATURE (°C)
FLASH CURRENT ACCURACY (%)
7550-25 0 25
-1.0
-0.5
0
0.5
1.0
1.5
2.0
2.5
-1.5
-50 100
VIN = 3.6
VIN = 5V
ILED = 500mA
LED TORCH CURRENT ACCURACY
vs. LOAD CURRENT (DAC MODE)
MAX77387 toc74
LED FLASH CURRENT SETTING (mA)
LED TORCH CURRENT ACCURACY (%)
20015010050
2
4
6
8
10
12
0
0 250
ILED2
ILED1 VIN = 3.6V
TORCH CURRENT ACCURACY
vs. TEMPERATURE (DAC MODE)
MAX77387 toc76
TEMPERATURE (°C)
TORCH CURRENT ACCURACY (%)
7550250-25
1.0
2.0
3.0
4.0
5.0
6.0
0
-50 100
VIN = 3.6V
VOUT = 5V
ILED = 125mA
LED TORCH CURRENT ACCURACY
vs. LOAD CURRENT (PWM MODE)
MAX77387 toc75
LED FLASH CURRENT SETTING (mA)
LED TORCH CURRENT ACCURACY (%)
20015010050
-2
-1
0
1
2
3
4
5
6
-3
0 250
ILED2
ILED1
VIN =3.6V
SHUTDOWN CURRENT vs. TEMPERATURE
MAX77387 toc77
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
7550250-25
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
-50 100
VIN = 3.6V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
26Maxim Integrated
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = 3.6V, TA = +25NC, unless otherwise noted.
SHUTDOWN CURRENT vs. INPUT VOLTAGE
MAX77387 toc78
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
5.04.54.03.53.0
10
20
30
40
50
60
70
0
2.5 5.5
SUPPLY CURRENT vs. INPUT VOLTAGE
(4MHz, FREQUENCY SCALING, SKIP ALLOWED)
MAX77387 toc79
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
5.04.54.03.53.0
200
400
600
800
1000
1200
0
2.5 5.5
SUPPLY CURRENT vs. INPUT VOLTAGE
(4MHz FPWM WITH FREQUENCY SCALING)
MAX77387 toc80
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
4.03.53.0
05
10
15
20
25
30
0
2.5 4.5
VOUT = 4.5V
4MHz FPWM
4MHz FPWM
WITH FREQUENCY SCALING
SUPPLY CURRENT vs. TEMPERATURE
(2MHz FPWM, 4MHz FPWM)
MAX77387 toc82
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
5
10
15
20
25
30
0
VIN = 3.2V
VOUT = 4.5V
2MHz FPWM
4MHz FPWM
7550250-25-50 100
SUPPLY CURRENT vs. TEMPERATURE
(4MHz, FREQUENCY SCALING, SKIP ALLOWED)
MAX77387 toc81
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
7550250-25
470
475
480
485
490
495
500
505
510
465
-50 100
VIN = 3.2V
VOUT = 4.5V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
27Maxim Integrated
Bump Description
Bump Configuration
PIN NAME FUNCTION
A1 LX_A Inductor Connection for Phase A. Connect LX_A to the switched side of the inductor and to the phase A
synchronous rectifier. LX_A is internally connected to the drain of the internal low-side MOSFET.
A2 PGND_A
Power Ground for DC-DC Converter Phase A. Connect to PGND (A2 and A4 together) as close as
possible to the IC. Make a star connection between input and output capacitors to ensure a short
ground loop. Connect to the common ground plane of the application.
A3 TORCH_EN Logic Input. Used to enable torch/flash mode (I2C programmable). TORCH_EN input has an optional
800kI pulldown resistor to AGND.
A4 PGND_B
Power Ground for DC-DC Converter Phase B. Connect to PGND (A2 and A4 together) as close as
possible to the IC. Make a star connection between input and output capacitors to ensure a short
ground loop. Connect to the common ground plane of the application.
A5 LX_B Inductor Connection for Phase B. Connect LX_B to the switched side of the inductor and to the phase B
synchronous rectifier. LX_B is internally connected to the drain of the internal low-side MOSFET.
MAX77387
TOP VIEW
(BUMP SIDE DOWN)
A
B
C
D
WLP
1234
LX_A PGND_A TORCH_EN PGND_B LX_B
OUT_A TX1_MASK TX2_MASK FLASH_STB OUT_B
VDD SCL REG_IN NTC IN
SDA FLED1 REG_IN FLED2 AGND
5
+
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
28Maxim Integrated
Pin Description (continued)
PIN NAME FUNCTION
B1 OUT_A
DC-DC Step-Up Converter Output Voltage for Phase A. Bypass this output using a ceramic capacitor.
See the Output Capacitor Selection section. Ensure that (B1) is directly connected to the output
capacitor and not to the REG_IN bumps (C3 or D3). This ensures lowest output ripple current of the
FLED current regulators. During shutdown OUT_A is high impedance.
B2 TX1_MASK Logic Input. TX1_MASK input has an optional 800kI pulldown resistor to AGND.
B3 TX2_MASK Logic Input. TX2_MASK input has an optional 800kI pulldown resistor to AGND.
B4 FLASH_STB Logic Input. Used to enable flash/torch mode (I2C programmable). FLASH_STB input has an optional
800kI pulldown resistor to AGND.
B5 OUT_B
DC-DC Step-Up Converter Output Voltage for Phase B. Bypass this output using a ceramic capacitor.
See the Output Capacitor Selection section. Ensure that (B5) is directly connected to the output
capacitor and not to the REG_IN bumps (C3 or D3). This ensures the lowest output ripple current of the
FLED current regulators. During shutdown OUT_B is high impedance.
C1 VDD Voltage for SDA/SCL Logic Levels. The I2C registers are reset when VDD is low.
C2 SCL I2C Clock Input. Data is read on the rising edge of SCL.
C3, D3 REG_IN
Input Supply for Current Regulators. Connect directly to the output capacitors. Make sure not to share
the trace between OUT_ and the capacitor since this results in increased output ripple current on the
LED output.
C4 NTC
NTC Bias Output. NTC provides 200FA to bias the NTC thermistor. The NTC voltage is compared to
the trip threshold programmed by the NTC_CNTL register. NTC is high impedance during shutdown.
Connect NTC to IN if not used.
C5 IN Input supply. Connect input bypass capacitor close to this input and AGND.
This input is used for low noise supply for internal bias as well as for the MAXFLASH function.
D1 SDA I2C Data Input. Data is read on the rising edge of SCL and data is clocked out on the falling edge of
SCL.
D2 FLED1
Flash LED1. High-side current regulator output. Current flowing out of FLED1 is based on I2C register
settings. Connect FLED1 to the anode of a flash LED or LED module. Optionally connect FLED1 and
FLED2 together for driving a single LED module. Connect FLED1 to REG_IN if not used. FLED1 is high
impedance during shutdown.
D4 FLED2
Flash LED2. High-side current regulator output. Current flowing out of FLED2 is based on I2C register
settings. Connect FLED2 to the anode of a flash LED or LED module. Optionally connect FLED1 and
FLED2 together for driving a single LED module. Connect FLED2 to REG_IN if not used. FLED2 is high
impedance during shutdown.
D5 AGND Analog Ground. Connect to common ground plane of the application.
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
29Maxim Integrated
Figure 1. Detailed Block Diagram and Typical Application Circuit
MAX77387
PGND_A
LX_A
LX_B
PGND_B
IN
AGND
VDD
SDA
LOGIC
INTERFACE
OUT_A
OUT_B
REG_IN
REG_IN
FLED1
FLED2
10µF
10V
0402
10µF
10V
0402
0.1µF
6.3V
0201
0.47µF
0.47µF
10µF
10V
0402
PWM LOGIC
REVERSE BLOCKING
REVERSE BLOCKING
PWM LOGIC
PEAK INPUT
CURRENT LIMIT
PEAK INPUT
CURRENT LIMIT
DCDC
SOFT-START
ADAPTIVE
OUTPUT
CONTROL
REGISTERS
UVLO AND
MAXFLASH
SELECT
MIN
PWM
COMP
PWM
COMP
ERROR
AMP
DAC
SLOPE AND RAMP
COMPENSATION
SLOPE AND RAMP
COMPENSATION
FREQUENCY
SCALING
SCL
TX1_MASK
TX2_MASK
TORCH_EN
FLASH_STB
NTC
I2C
INTERFACE
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
30Maxim Integrated
Detailed Description
The MAX77387 flash driver IC integrates a dual-phase
2.0A adaptive PWM step-up DC-DC converter and two
high-side 1A current regulators for LED camera flash and
torch applications. All aspects of the device for torch and
flash can be controlled through an I2C interface.
Modes of Operation
The IC has five modes of operation. See Figure 2.
Shutdown Mode
In shutdown mode, only the VDD input is active.
The IC enters shutdown mode when VDD is reduced
below the VDD_UVLO. When the IC enters shutdown
mode, all I2C registers are reset.
If VDD increases above the VDD_UVLO threshold, the IC
exits shutdown mode and enters standby mode.
Standby Mode
In standby mode, the I2C interface is active and trigger
inputs are also active if defined by I2C register (TORCH_
EN and FLASH_STB).
The IC enters standby mode from active mode when the
DC-DC converter is disabled or in the case where the
input voltage is below the IN_UVLO.
If the current regulators are enabled (torch or flash mode)
or the DC-DC converter is enabled (in either normal
mode, dropout mode), then the IC enters active mode.
The input voltage must also be above IN_UVLO for the
transition from standby to active mode to occur. If the IN
is below the IN_UVLO, the IC remains in standby mode.
Active Mode
In active mode, the DC-DC converter is enabled and
operating in the boost mode set by the DCDC_MODE
bits. The current regulators are disabled.
While in active mode, if either current regulator is
enabled, then the IC enters torch or flash mode.
Torch Mode
In torch mode, the current regulator is enabled according
to the torch settings.
The IC continues to operate in torch mode when the torch
current regulator is enabled and the flash current regula-
tor is not enabled.
If flash mode is enabled for a current regulator, that
regulator mode enters flash mode since flash mode has
a higher priority.
If the current regulator is disabled, then the IC returns to
active mode.
Flash Mode
In flash mode, the current regulator is enabled according
to the flash settings.
Once the flash event ends, the IC can either enter torch
mode or active mode depending on the torch settings.
Figure 2. Modes of Operation
SHUTDOWN STANDBY
VDD = LOW
VDD = IN_UVLO
ACTIVE TORCH MODE
IN > IN_UVLO OR
(DCDC_MODE ≠ 00 OR
LED CURRENT REGULATOR
ENABLED)
FLASH MODE
ENABLED
FLASH MODE
DISABLED
IN < UVLO AND
(DCDC_MODE = 00 AND
LED CURRENT REGULATOR
DISABLED)
FLASH
MODE
TORCH MODE
ENABLED
TORCH MODE
DISABLED
FLASH MODE ENABLED
AND TORCH MODE ENABLED
FLASH MODE DISABLED
AND TORCH MODE ENABLED
P IN_UVLO
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
31Maxim Integrated
Adaptive Output Voltage Regulation
The IC uses an adaptive voltage scheme to optimize
system efficiency based on the forward voltage of the
populated LED. To ensure that the DC-DC converter is
operating in a stable condition and that the current regu-
lators are providing the correct output current levels, the
voltages across the current regulators are sampled to
determine whether the output voltage of the DC-DC con-
verter needs to be increased or decreased.
The adaptive control loop controls an internal 9-bit DAC
that sets the output voltage of the DC-DC converter.
During a torch or flash event, the DC-DC converter con-
tinuously adapts its output voltage up or down by one
DAC LSB (VADPT_REG_STEP) every 1Fs during soft-
start, and every 8Fs during normal operation.
During the torch or flash event, the DC-DC converter
output voltage is logged and then stored in both the
DCDC_OUT and DCDC_OUT_MAX registers.
The DCDC_OUT register is used to store the value of the
DC-DC converter output voltage just before the current
regulator is disabled. The DCDC_OUT_MAX register is
used to store the maximum value of the DC-DC con-
verter output voltage that occurred during the torch or
flash event. The information stored in these two registers
allows the user to predict the forward voltage of the LED
for diagnostics.
In certain cases, the adaptive control loop operation is
limited. During minimum duty cycle operation, the DC-DC
converter output voltage is only allowed to increase
to ensure correct operation. During the time when the
DC-DC converter is operating at the peak input current
limit, the DC-DC converter output voltage is only allowed
to decrease since increasing the output voltage would
require a greater input current than is allowed.
If the adaptive control loop attempts to increase the
DC-DC converter output voltage above the OVP_D volt-
age level, then the output voltage is maintained at this
level for the duration of the OVP_D debounce time. If the
adaptive control loop continues to attempt to increase the
output voltage above the OVP_D voltage level after the
OVP_D debounce timer expires, then this is an indication
that the LED forward voltage is too high for the IC or the
LED is not correctly installed.
Current Regulator Voltage Headroom
The current regulator headroom is selectable between
+120mV to +210mV in 30mV steps. This allows the user
to optimize for either efficiency or accuracy.
Lowering the voltage headroom of the current regulator
reduces the accuracy and the PSRR of the current regu-
lator while improving the system efficiency.
Increasing the voltage headroom of the current regula-
tor improves the accuracy and the PSRR of the current
regulator while reducing the system efficiency.
Step-Up Converter
The IC includes a dual-phase PWM step-up converter
that supplies power to the flash LEDs. The output volt-
age can be adaptively controlled based on the forward
voltage of the installed LEDs. The step-up converter
switches an internal power MOSFET at frequencies up to
4MHz (per phase), resulting in a maximum output ripple
frequency of 8MHz, with a duty cycle that can vary from
3.125% to 75% to maintain constant output voltage as
VIN and load vary. Internal circuitry prevents any unwant-
ed subharmonic switching by forcing a minimum duty-
cycle. Alternatively, the converter can be programmed to
enter skip mode for light load conditions to ensure high
efficiency for low output current operation.
Dual-Phase Operation
The advantage of the IC dual-phase control architecture
is that the effective switching frequency is doubled. This
provides a significant reduction in the output voltage
ripple, hence reducing stress on the output capacitor.
Lowering the output voltage ripple also lowers the output
current ripple of the current regulator, resulting in lower
EMI for the system.
For high-current applications such as LED flash, the dual
phase scheme also helps reduce the inductor size. For
example, a traditional single-phase architecture requiring
an input current of 3A and an inductor saturation current
of 3A would require and inductor sized approximately
5mm x 5mm with a height of 1mm. By going to a dual-
phase architecture the 5x5mm inductor can be replaced
by two 1.8mm x 1.0mm inductors to significantly reduce
the total solution size. In addition, the second advantage
is inductor saturation current (per phase) could be low-
ered to 1.8A.
Skip Mode
In PWM operation, the DC-DC converter switches cycles
continuously. When SKIP mode is enabled, the DC-DC
converter can disable a switching cycle if the output volt-
age is sufficiently high. When this condition is detected,
the next switching cycle is skipped. The peak inductor
current value is chosen to be high enough so that suf-
ficient energy is transferred to the output in a burst of
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
32Maxim Integrated
switching-cycles that occur less frequently to improve
the overall efficiency. However, the output voltage ripple
in this mode increases.
Noise-sensitive applications that cannot tolerate the
increased output voltage ripple can disable skip mode to
force continuous PWM operation. See the DCDC_CNTL2
register.
Current Sharing
For multiphase converters one of the critical parameters
is current sharing. If good balance between the phases is
not ensured, then one phase could potentially be forced
to handle a disproportionate amount of the total output
current, resulting in overheating and loss of efficiency.
The IC uses a common peak current mode control
scheme that inherently provides current balancing
between the phases.
Switching Frequency Selection
The DC-DC converter can be programmed to oper-
ate at several different fixed switching frequencies.
Alternatively, the DC-DC converter can be programmed
to automatically select the optimal switching frequency
based on the operating duty cycle. Optimized frequency
selection allows the DC-DC converter to operate at the
highest available switching frequency for the lowest
required duty cycle. See the DCDC_CNTL2 register.
Overvoltage Protection
The IC provides two overvoltage protection mechanisms.
The primary protection mechanism (OVP_D), which is
part of the adaptive regulation control, limits the DCDC
converter output voltage to the OVP_D threshold for a
time duration of tOVP_D before the DC-DC converter and
current regulators are disabled.
A secondary protection mechanism (OVP_A) limits the
DC-DC converter output voltage to the OVP_A threshold
that is set higher than the OVP_D threshold, but has a
much reduced time duration. If the DC-DC converter out-
put voltage rises above the OVP_A threshold, the DC-DC
converter and current regulators are disabled with mini-
mum time delay.
True Shutdown
When the IC is in standby mode, the DC-DC converter is
disabled where both the high side and low side switches
are turned off. In addition, the high-side switch’s rectifier
is reversed biased putting the DC-DC converter output
into a high-impedance state, allowing the output to dis-
charge to ground.
Soft-Start
When the input supply is initially applied to the IC, the
output is in true shutdown mode, meaning that the out-
put DC-DC converter remains at high impedance. Upon
entering active mode the following steps are imple-
mented to ensure a controlled soft-starting of the DC-DC
converter output.
The soft-start steps are:
1) Precharge
When entering precharge, the output voltage is
unknown since it was in high impedance. If the high-
side switch is simply forced on, this can result in a
large inrush of current. To avoid this, the high-side
switch switches at a 25% duty cycle resulting in a
controlled precharge of the output.
The precharge is completed once the output voltage
reaches VIN - 300mV.
If the load on the output exceeds 10mA while pre-
charging, the DC-DC converter remains in precharge
mode and the output is unable to reach VIN - 300mV.
2) Ramping of the output voltage
In this mode, the output is ramped to DCDC_SS level.
The output is ramped at a rate of 1LSB per 1Fs, result-
ing in 6.25mV/Fs ramp rate.
For DCDC_MODE = 00 (low-power adaptive mode), the
output does not soft-start before the trigger event. When
a torch or flash event is triggered the DC-DC converter
first performs step 1, followed by step 2. After the DC-DC
converter output is ramped to the DCDC_SS level, the
current regulator is then ramped according to the pro-
grammed ramp values.
For DCDC_MODE = 01 (prebiased adaptive mode),
when setting this mode, the DC-DC converter first per-
forms step 1, followed by step 2. Once step 2 is com-
pleted the DC-DC converter continues to regulate the
output at DCDC_SS level.
Once a torch or flash event is triggered, the current regu-
lator is enabled with minimum delay since the output is
already precharged. The output current ramps according
to the programmed ramp values. Once the current regu-
lator is disabled the output continues to regulate at the
DCDC_OUT level. Upon a new torch or flash event the
output continues from this DCDC_OUT level.
For DCDC_MODE = 10 (fixed voltage mode), when set-
ting this mode, the DC-DC converter first performs step
1, followed by step 2. Once step 2 is completed the
DC-DC converter continues to regulate the output at the
DCDC_SS level, regardless of status of torch and flash
modes.
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
33Maxim Integrated
Figure 3. DC-DC Converter Soft-Start for DCDC_MODE = 00
Figure 4. DC-DC Converter Soft-Start for DCDC_MODE = 01
ILX
VOUT
IFLED
TRIGGER EVENT
TRIGGER
EVENT
DCDC_SS
VIN
tBIAS_RDY
tTORCH_EN_STDBY
tOUT_PCHG
tDCDC_SS RAMP-UP TIME RAMP-DOWN TIME STEP 1
STEP 3
STEP 2
ILX
VOUT
IFLED
DCDC_SS
tDCDC_SS
MODE = STANDBY MODE = ACTIVE
DCDC_MODE = 01
tBIAS_RDY
tSTDBY2ACTIVE
tOUT_PCHG
tTORCH_EN_ACTIV OR
tFLASH_EN_ACTIV
RAMP-UP TIME RAMP-DOWN TIME
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
34Maxim Integrated
Figure 5 DC-DC Converter Soft-Start for DCDC_MODE = 10
Figure 6. DC-DC Converter Soft-Start for DCDC_MODE = 11
ILX
VOUT
IFLED
DCDC_SS
MODE = STANDBYMODE = ACTIVE
DCDC_MODE = 11
tBIAS_RDY
tSTDBY2ACTIVE
tOUT_PCHG tDCDC_SS
MODE = STANDBYMODE = ACTIVE
DCDC_MODE = 10
tBIAS_RDY
tSTDBY2ACTIVE
tOUT_PCHG
ILX
VOUT
VIN
IFLED
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
35Maxim Integrated
For DCDC_MODE = 11 (dropout mode), when setting this
mode, the DC-DC converter first performs step 1, after
which, the high-side switch is turned on 100%, regard-
less of the status of torch and flash modes.
The time it takes from triggering torch or flash mode until
the current is at final value depends on the following
conditions:
U If the time spent in standby mode is shorter than the
internal bias, tBIAS_RDY, then the bias needs to come
up before anything happens.
U The time duration of the soft-start is dependent on the
input voltage and initial charge of the output capaci-
tor, tOUT_PCHG.
U The higher the programmed voltage level results in a
longer start time (tDCDC_SS). The output is ramped at a
rate of 1LSB per 1Fs, resulting in a 6.25mV/Fs ramp rate.
U The regulator output current is ramped according to
the programmed ramp rate in flash or torch mode.
Therefore, the final value of the output current impacts
the time duration it takes to ramp the current from
0mA to the final value.
End of Trigger Event
When the DC-DC converter is disabled, the setting of the
DCDC_MODE determines the method to discharge the
output.
The discharge steps are:
1) The DC-DC converter continues switching the high-
side switch at 25% duty cycle allowing for the output
to be a controlled discharge. During this step, the
energy in the output capacitor is gradually transferred
from the output capacitor back to the input capacitor,
ensuring that the energy is conserved. Step 1 is com-
pleted once the output voltage reaches VIN + 200mV.
2) The DC-DC converter high-side switch goes from
25% switching to 100% (dropout mode). This allows
the output to be discharged to within VIN + 150mV.
3) The DC-DC converter transitions from operating in
dropout mode to true shutdown mode. In true shut-
down mode, the output is high impedance.
For DCDC_MODE = 00, the DCDC converter goes
through all three steps listed above. This ensures that the
output is discharged to within VIN +150mV.
For DCDC_MODE = 01, 10, or 11, the DC-DC converter
is not disabled therefore the output is not discharged. To
disable the DC-DC converter, set DCDC_MODE = 00.
The following describes the end of trigger event when
coming from the different modes 01, 10, or 11 to 00.
Coming from DCDC_MODE = 01 or 10 to 00, the DC-DC
converter goes through all three steps listed above. This
ensures that the output is discharged to within VIN +
150mV.
Coming from DCDC_MODE = 11 to 00, the DC-DC con-
verter enters true shutdown mode since the output is
equal or lower than the input voltage.
Gain Selection
The gain of the error amplifier of the DC-DC converter
determines the load regulation performance as well as
setting the minimum output capacitor value required
for stable regulation. Lowering the gain results in larger
load regulation and a decreased output capacitor value
requirement.
The following DCDC_GAIN settings are available:
U DCDC_GAIN = 0 sets the lowest gain.
U DCDC_GAIN = 1 sets the highest gain.
For output capacitor values, see the Output Capacitor
Selection section.
Low-Side Current Limit
The IC provides a programmable current limit for the
low-side switch. This current limit functions as an input
current limit, and is critical for the application since this
is the function that determines the maximum current that
can be drawn from the input supply. The low side current
limit is also important for the choice of inductor since this
determines the minimum saturation current.
If the input current limit is reached during operation,
the low-side switch terminates the cycle and turns on
the high-side switch. When minimum tON condition is
reached the duty cycle is limited and the LX peak current
might exceed the current limit setting slightly. This results
in a drop of the output voltage. The DC-DC converter
can operate in continuous input current limit condition.
However, due to the drop in output voltage the current
regulator parameters cannot be guaranteed in this mode
of operation.
Current Regulator LED
The IC has two high-side regulators that can be used for
torch and flash modes with the settings:
U Flash mode from 15.625mA to 2000mA (1000mA for
each current regulator) in 15.625mA steps total
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
36Maxim Integrated
U Torch mode with DAC mode enabled from 3.91mA to
500mA (250mA for each current regulator) in 3.91mA
steps total
U Torch mode with PWM mode enabled from 125mA
to 1000mA in 125mA steps for PWM dimming with
programmable duty cycle from 3.125% to 25% in
3.125% steps.
The regulator sources current out of the FLED output,
and is always powered from REG_IN.
If both torch and flash are enabled for LED current regu-
lator, flash mode always has the highest priority.
Each current setting is controlled by I2C interface.
For applications requiring higher output current, the two
current regulators can be connected in parallel, doubling
the output current capability. The total current flowing
though the LED is the sum of the programmed FLED1
and FLED2 current. The ramp rate is doubled compared
to the dual LED application. If one of the LED current lev-
els is set higher than the other the ramp rate, decrease to
1x as soon as the lower LED current regulator has com-
pleted its ramp function. It is therefore recommended
that the current settings for FLED1 and FLED2 are set to
the same rate of maximum of 1LSB in difference. It is not
recommended to use PWM dimming when FLED1 and
FLED2 are connected since the LED current regulators
are not synchronized together.
When FLED1 and FLED2 are connected together, the
adaptive control monitors the voltage headroom for each
of the current regulators. Since the two FLED pins are
connected together, the required output voltage of the
FLED1/FLED2 is the same. The adaptive control scheme
regulates the voltage across the current regulator to
be the preset value. In this case, the required VOUT for
FLED1 and FLED2 are the same.
DAC and PWM Dimming
Dimming control of the current regulators can be
achieved using DAC control, PWM control or a combina-
tion of both.
DAC Control
When DAC control is used, the current regulators are set
to a constant preprogrammed value.
PWM Control
When PWM control is used, the current regulators
are enabled/disabled at a predetermined frequency,
FREQ_PWM[1:0]. The ratio between the on and off times
determines the percentage of full-scale current that each
current regulator outputs.
Using PWM dimming with high frequency and low duty
cycle increases the output error due to rise and fall time
and becomes a significant part of the total on time. It is
therefore not recommended to operate at high frequency
and low duty cycle.
DAC and PWM Control
DAC and PWM control can be used at the same time. For
example, in torch mode the full-scale current can be set
with the DAC, and then PWM control used to establish
a much lower average current. Typically, this is done to
eliminate the color shift seen when using a high-current
LED at a low DC current setting.
Figure 7. Driving Two LED Configuration Figure 8. Driving a Single LED Configuration
REG_IN
REG_IN
FLED1
FLED2
MAX77387
REG_IN
REG_IN
FLED1
FLED2
MAX77387
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
37Maxim Integrated
Ramp Control
Each current regulator has a ramp function that is
engaged every time the current regulator is enabled/
disabled or the output current level is changed. This is
done to control the EMI of the current regulator output.
The ramping of the current regulator is done by ramping
one LSB step of the current regulator per the internal
clock, providing a staircase ramp of the output current.
For flash mode, the output current increases in 15.625mA
steps from 15.625mA until the final value.
For torch mode the output current increases in 3.91mA
steps from 3.91mA until final value.
The actual time used for ramping up and down are deter-
mined by the following equations.
For flash mode:
FLASH_UP
FLASH_RU
t (IFLASH)
IFLASH_MAX
=
FLASH_DOWN
FLASH_RD
t (IFLASH)
IFLASH_MAX
=
where:
FLASH_RU is the total ramp-up time.
FLASH_RD is the total ramp-down time.
IFLASH is the programmed flash current.
IFLASH_MAX is the maximum programmable flash current
(1000mA).
For torch mode in DAC mode:
TORCH_DAC_UP
TORCH_RU
t (ITORCH_DAC)
ITORCH_DAC_MAX
=
TORCH_DAC_DOWN
TORCH_RD
t (ITORCH_DAC)
ITORCH_DAC_MAX
=
where:
TORCH_RU is the total ramp-up time.
TORCH_RD is the total ramp-down time.
ITORCH_DAC is the programmed DAC mode torch current.
ITORCH_DAC_MAX is the maximum programmable DAC
mode torch current (250mA).
For torch mode in PWM mode:
TORCH_PWM_UP
TORCH_RU
t (ITORCH_PWM)
ITORCH_PWM_MAX
=
TORCH__PWM_DOWN
TORCH_RD
t (ITORCH_PWM)
ITORCH_PWM_MAX
=
where:
TORCH_RU is the total ramp-up time.
TORCH_RD is the total ramp-down time.
ITORCH_PWM is the programmed PWM mode torch cur-
rent.
ITORCH_PWM_MAX is the maximum programmable PWM
mode torch current (1000mA).
Torch and Flash Safety Timer
The torch/flash safety timers are activated any time torch/
flash mode is respectively enabled.
The torch safety timer, programmable from 122.9ms to
22s through I2C, limits the duration of the torch mode in
case the torch mode is not disabled through logic control
or I2C within the programmed torch safety timer duration.
The flash safety timer, programmable from 0.256msec
to 699.392ms through I2C, limits the duration of the flash
mode in case the flash is not disabled through logic
control or I2C within the programmed flash safety timer
duration.
The flash mode timers operate in either one-shot time
mode or maximum duration timer mode or PWM timer
mode.
The torch mode timers operate only in one-shot time
mode. There is a torch mode register setting to disable
the timer potentially allowing for indefinite torch mode
duration. See Figure 11. See the TORCH_TMR_CNTL[7]
register. In maximum flash mode, the trigger input is
level triggered, and the timer is only ensuring that the
maximum duration of the flash is limited to the prepro-
grammed threshold.
Time duration includes current ramp-up time, but not
ramp down time.
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
38Maxim Integrated
Figure 10. One-Shot Torch/Flash Timer Mode
Figure 9. Maximum Flash Timer Mode/Disabled Torch Timer Mode
OUTPUT
CURRENT
ENABLING OF
TORCH MODE
ONE SHOT TORCH/FLASH TIMER
ONE SHOT TORCH/
FLASH TIMER
Figure 10
MAXIMUM FLASH TIMER
OUTPUT
CURRENT
ENABLING OF
FLASH MODE
MAXIMUM FLASH
SAFETY TIMER
OUTPUT
CURRENT
ENABLING OF
TORCH MODE
DISABLED
SAFETY TIMER
A. MAXIMUM FLASH TIMER MODE
B. DISABLED TORCH TIMER MODE
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
39Maxim Integrated
MAXFLASH Function
During high load currents on a battery cell, the battery
voltage momentarily drops due to internal ESR of the
battery in series with impedance between the battery
and the load.
For equipment requiring a minimum voltage for stable
operation, the ESR of the battery needs to be calculated
to estimate the maximum current that can be drawn from
the battery without making the cell voltage drop below
this critical minimum system voltage level.
If the system is not able to accurately predict the true
ESR and impedance of the system, the minimum opera-
tional battery voltage has to be increased to guard band
for tolerances and operating conditions.
In addition, a smartphone includes multiple applica-
tions that are operating asynchronously with the camera
flash application. Therefore, it is difficult to predict the
load current on the battery at any given time that would
require additional guard banding of the battery voltage to
insure that a sufficient system voltage is provided during
worst case conditions.
The MAXFLASH 2.0 function eliminates the requirement
for predicting the battery voltage during flash events. The
MAXFLASH 2.0 monitors the input voltage while compar-
ing it against a user defined voltage threshold. If the input
voltage drops below this user defined threshold, referred
to as MAXFLASH_TH, the current regulator output cur-
rent is reduced by one step. After a given time, referred
to as LB_TMR_F, the input voltage is compared against
the MAXFLASH_TH threshold again. If the input voltage
is still below the MAXFLASH_TH threshold, the current
regulator output current is once again reduced by one
step to ensure that the minimum operational voltage is
available for the rest of the system. However, if the input
voltage is near the MAXFLASH_TH threshold plus a user
defined hysteresis, referred to as MAXFLASH_HYS, the
current regulator output current is increased by one
step, but only if the current regulator out¬put current
is less than the user defined output current setting. In
the event that MAXFLASH_HYS is set to 000, the flash
current can only be reduced as a result of a low system
battery voltage regardless of whether or not the system
voltage recovers. This continues for the entire duration
of the flash/torch event, ensuring that the current regula-
tor output current is always maximized for the specific
operational conditions.
If the MAXFLASH 2.0 function is triggered during a
torch or flash event, the MAXFLASH bit in the STATUS2
register is set. In the case of a MAXFLASH event, the
MAX77387 logs the lowest current setting reached for
each current regulator during the torch or flash event.
This information is stored in both the MAXFLASH3 and
MAXFLASH4 registers. This information can be used to
determine whether the reduction in LED light has been
sufficient or if the picture quality has been compromised.
TX_MASK
In the typical application there are several other applica-
tions that can draw large peak currents from the battery
that are also supplying the flash driver.
Since the current from the battery has to be limited to
protect the battery from getting damaged, the IC has two
logic inputs that can be used to limit the flash current dur-
ing high current events, such as GSM Tx or WCDMA Tx.
The TX1_MASK and TX2_MASK can be used to limit the
maximum current for the LED by setting the maximum
allowed flash current during Tx event. If TX1_MASK and
TX2_MASK are triggered at the same time, the current is
limited by the TX1_MASK. Once the TX1_MASK event is
no longer present, output current is limited by TX2_MASK
if this event is still valid.
Once a TX_MASK event is triggered the output current is
reduced within the tTX_MASK_EN to ensure that the cur-
rent draw from the battery does not exceed the maximum
allowed for the battery.
Once the TX_MASK event is no longer present the output
current is ramped from the reduced value to normal flash
current level according to the ramp up for flash mode.
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
40Maxim Integrated
NTC Control
An NTC input is provided for the (optional) finger-burn
protection feature. To use this feature, connect a nega-
tive temperature thermistor (NTC) between NTC and
AGND.
In flash mode, the IC sources 200FA current out of the
NTC pin, and the voltage established by this current and
the NTC resistance is compared internally to a voltage
threshold in the range of 200mV to 550mV, programmed
through bits NTC_TH_FLASH[2:0]. If the voltage on the
NTC pin falls below the programmed threshold during
a flash event, the flash cycle is immediately terminated,
and an indication is latched into the Status 2 register. To
disable this function, clear NTC_EN bit in the NTC Control
registers.
In torch mode, the IC pulses a 200FA current out of the
NTC pin, and the voltage established by this current and
the NTC resistance is compared internally to a voltage
threshold in the range of 200mV to 550mV, programmed
through bits NTC_TH_TORCH[2:0]. If the voltage on the
NTC pin falls below the programmed threshold during a
torch event, the torch cycle is immediately terminated,
and an indication is latched into the Status 2 register. To
disable this function, clear NTC_EN bit in the NTC Control
registers.
The NTC pulse time is defined by tNTC_TORCH_ON and
tNTC_TORCH_OFF. The NTC biased current is pulsed in
torch mode to ensure low power dissipation of the NTC
resistor as well as saving current.
Figure 11. TX1_MASK or TX2_MASK During Flash Mode
Figure 12. TX1_MASK and TX2_MASK Occurring at Same Time
256
tTX_MASK_EN
IFLED1
IFLED2
FLASH1[6:0]
FLASH2[6:0]
FLASH_TX1_MASK[5:0]
OR
FLASH_TX2_MASK[5:0]
tFLASH_UP =FLASH_RU (IFLED−(FLASH_TX1_MASK OR FLASH_TX2_MASK))
TX1_MASK OR
TX2_MASK
Figure 11
256
tTX_MASK_EN
IFLED1
IFLED2
FLASH1[6:0]
FLASH2[6:0]
tFLASH_UP =FLASH_RU (IFLED−(FLASH_TX1_MASK–FLASH_TX2_MASK))
256
tFLASH_UP =FLASH_RU (FLASH_TX2_MASK))
TX1_MASK
TX2_MASK
FLASH_TX1_MASK[5:0]
FLASH_TX2_MASK[5:0]
Figure 12
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
41Maxim Integrated
Due to self-heating of the IC, the NTC bias current chang-
es. This can be compensated for by calculating what
the expected temperature is for the IC, and therefore,
what the exact NTC bias current is. Doing this provides a
higher accuracy for the thermal sensing:
TJ = TA + BJAx(VOUTxIOUTxE)
where:
TA is the ambient temperature.
BJA is 46NC/W (determined by the package type).
VOUT is the expected output voltage for given setting.
IOUT is the programmed output current for the given
setting.
E is the system (DCDC converter + current regulator)
efficiency.
Once the TJ is calculated then the correct NTC bias cur-
rent level can be calculated:
NTC_BIAS = NTC_BIAS_25C + NTC_T_COM x(Tj-25)
where:
NTC_BIAS is the output bias current for given junction
temperature.
NTC_BIAS_25C is the bias current at TA = +25NC.
NTC_T_COM is the temperature compensation factor.
Short and Open LED Detection
The IC includes a comparator that detects if the LED out-
put is shorted. If the voltage across the LED is less than
1V, then bit[7:6] in STATUS1 is set after the debounce
time expires, LED1_SHORT, LED2_SHORT. When the IC
detects the short, only that current regulator is disabled.
If an LED becomes open-circuit during adaptive loop
control operation, then VREG_IN increases until the
OVP_D threshold is reached. The OVP_D event is logged
in STATUS1 after the debounce timer expires. When an
OVP_D condition exists the regulator and DC-DC con-
verter is disabled
Thermal Shutdown
Thermal shutdown limits total power dissipation in the
IC. When the junction temperature exceeds +160NC
(typ), the device turns off, allowing the IC to cool. See
STATUS1 register.
When a thermal shutdown condition exists the regulator
and DC-DC converter is disabled.
I2C Serial Interface
An I2C-compatible, 2-wire serial interface controls the
step-up converter output voltage, flash and torch current
settings, flash duration, and other parameters. The serial
bus consists of a bidirectional serial-data line (SDA) and
a serial-clock input (SCL). The IC is a slave-only device,
relying upon a master to generate a clock signal. The
master initiates data transfer to and from the IC and gen-
erates SCL to synchronize the data transfer (Figure 13).
I2C is an open-drain bus. Both SDA and SCL are bidi-
rectional lines, connected to a positive supply voltage
through a pullup resistor. They both have Schmitt triggers
and filter circuits to suppress noise spikes on the bus to
assure proper device operation. A bus master initiates
communication with the IC as a slave device by issuing
a START condition followed by the IC’s address. The
IC’s address byte consists of 7 address bits and a read/
write bit (R/W). After receiving the proper address, the IC
issues an acknowledge bit by pulling SDA low during the
ninth clock cycle.
Figure 13. 2-Wire Serial Interface Timing Detail
SDA
SCL
START CONDITION REPEATED START CONDITION START CONDITIONSTOP CONDITION
tHD,STA
tHD,DAT
tSU,DAT
tSU,STA
tSU,STO
tBUF
tHD,STA
tLOW
tHIGH
tRtF
Figure 13
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
42Maxim Integrated
I2C Slave Address
The IC acts as a slave transmitter/receiver. Its slave
address is 0x94h for write operations and 0x95h for read
operations.
I2C Bit Transfer
Each data bit, from the most significant bit to the least
significant bit, is transferred one by one during each
clock cycle. During data transfer, the SDA signal is
allowed to change only during the low period of the SCL
clock and it must remain stable during the high period of
the SCL clock (Figure 14).
START and STOP Conditions
Both SCL and SDA remain high when the bus is not busy.
The master signals the beginning of a transmission with
a START (S) condition by transitioning SDA from high
to low while SCL is high. When the master has finished
communicating with the IC, it issues a STOP (P) condition
by transitioning SDA from low to high while SCL is high.
The bus is then free for another transmission (Figure 15).
Both START and STOP conditions are generated by the
bus master.
Acknowledge
The acknowledge bit is used by the recipient to hand-
shake the receipt of each byte of data Figure 16. After
data transfer, the master generates the acknowledge
clock pulse and the recipient pulls down the SDA line
during this acknowledge clock pulse so that the SDA
line stays low during the high duration of the clock pulse.
When the master transmits the data to the IC, it releases
the SDA line and the IC takes the control of the SDA line
and generates the acknowledge bit. When SDA remains
Figure 14. Bit Transfer
Figure 15. START and STOP Conditions Figure 16. Acknowledge
SDA
SCL
START CONDITION STOP CONDITION
Figure 15
SDA OUTPUT
FROM
TRANSMITTER
SDA OUTPUT
FROM
RECEIVER
SCL FROM
MASTER 1
NOT ACKNOWLEDGE
ACKNOWLEDGE
CLOCK PULSE FOR
ACKNOWLEDGEMENT
D7
START CONDITION
D6 D0
289
Figure 16
SCL
SDA
START
CONDITION
(S)
START
CONDITION
(S)
DATA LINE STABLE
DATA VALID
DATA ALLOWED
TO CHANGE
Figure 14
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
43Maxim Integrated
high during this 9th clock pulse, this is defined as the
not acknowledge signal. The master can then generate
either a STOP condition to abort the transfer, or a repeat-
ed START condition to start a new transfer.
Write Operations
The IC recognizes the write byte protocol as defined in the
SMBus specification and shown in section A of Figure 17.
The write byte protocol allows the I2C master device to
send 1 byte of data to the slave device. The write byte
protocol requires a register pointer address for the sub-
sequent write. The IC acknowledges any register pointer
even though only a subset of those registers actually
exists in the device.
The write byte protocol is as follows:
1. The master sends a start command.
2. The master sends the 7-bit slave address followed by
a write bit.
3. The addressed slave asserts an acknowledge by pull-
ing SDA low.
4. The master sends an 8-bit register pointer.
5. The slave acknowledges the register pointer.
6. The master sends a data byte.
7. The slave updates with the new data.
8. The slave acknowledges the data byte.
9. The master sends a STOP condition.
In addition to the write-byte protocol, the IC can write
to multiple registers as shown in section B of Figure 17.
This protocol allows the I2C master device to address the
slave only once and then send data to a sequential block
of registers starting at the specified register pointer.
Use the following procedure to write to a sequential block
of registers:
1. The master sends a start command.
2. The master sends the 7-bit slave address followed by
a write bit.
3. The addressed slave asserts an acknowledge by pull-
ing SDA low.
4. The master sends the 8-bit register pointer of the first
register to write.
5. The slave acknowledges the register pointer.
6. The master sends a data byte.
7. The slave updates with the new data.
8. The slave acknowledges the data byte.
Figure 17. Write to the IC
LEGEND
SLAVE TO MASTER
MASTER TO SLAVE
A. WRITING TO A SINGLE REGISTER WITH THE "WRITE BYTE" PROTOCOL
1711 88111
S0AAAP
SLAVE ADDRESS REGISTER POINTER DATA
NUMBER OF BITS
R/W
R/W
B. WRITING TO MULTIPLE REGISTERS
1711 881118
S0AA
AA
SLAVE ADDRESS REGISTER POINTER X DATA X
NUMBER OF BITS
DATA X+1
8811
AAP
DATA X+n-1 DATA X+n
NUMBER OF BITS
Figure 17
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
44Maxim Integrated
9. Steps 6 to 8 are repeated for as many registers in
the block with the register pointer automatically incre-
mented each time.
10. The master sends a STOP condition.
Read Operations
The method for reading a single register (byte) is shown
in section A of Figure 18. To read a single register:
1. The master sends a start command.
2. The master sends the 7-bit slave address followed by
a write bit.
3. The addressed slave asserts an acknowledge by pulling
SDA low.
4. The master sends an 8-bit register pointer.
5. The slave acknowledges the register pointer.
6. The master sends a repeated START condition.
7. The master sends the 7-bit slave address followed by
a read bit.
8. The slave assets an acknowledge by pulling SDA low.
9. The slave sends the 8-bit data (contents of the register).
10. The master assets an acknowledge by pulling SDA low.
11. The master sends a STOP condition.
In addition, the IC can read a block of multiple sequential
registers as shown in section B of Figure 18. Use the fol-
lowing procedure to read a sequential block of registers:
1. The master sends a start command.
2. The master sends the 7-bit slave address followed by
a write bit.
3. The addressed slave asserts an acknowledge by pulling
SDA low.
4. The master sends an 8-bit register pointer of the first
register in the block.
5. The slave acknowledges the register pointer.
6. The master sends a repeated START condition.
7. The master sends the 7-bit slave address followed by
a read bit.
8. The slave assets an acknowledge by pulling SDA low.
9. The slave sends the 8-bit data (contents of the register).
10. The master assets an acknowledge by pulling SDA low.
11. Steps 9 and 10 are repeated for as many registers
in the block, with the register pointer automatically
incremented each time.
12. The master sends a STOP condition.
Figure 18. Read from the IC
LEGEND
SLAVE TO MASTER
MASTER TO SLAVE
A. READING A SINGLE REGISTER
1711
88
711 11
S0AASr 1A
SLAVE ADDRESS REGISTER POINTER SLAVE ADDRESS
NUMBER
OF BITS
R/W R/W
NA PDATA
B. READING MULTIPLE REGISTERS
1711
88
711 11
S0AASr 1A
SLAVE ADDRESS REGISTER POINTER X SLAVE ADDRESS
NUMBER
OF BITS
NUMBER
OF BITS
R/W R/W
ADATA X
8
ADATA X+1
8
ADATA X+n-1
8
NA PDATA X+n
Figure 18
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
45Maxim Integrated
Table 1. I2C Register Map
ADDRESS REGISTER
NAME B7 B6 B5 B4 B3 B2 B1 B0
0x00 CHIP_ID1 DIE_TYPE[7:4] DIE_TYPE[3:0]
0x01 CHIP_ID2 DIE_DASH[3:0] DIE_REV[3:0]
0x02 STATUS1 LED1_SHORT LED2_SHORT REG_IN_UVLO IN_UVLO_
THERM
NTC_
THERM NTC_SHORT OVP_A OVP_D
0x03 STATUS2 MAXFLASH DONE TX1_MASK TX2_MASK FLASH_TMR TORCH_TMR ILIM nRESET
0x04 IFLASH1 FLASH1_EN FLASH1[5:0]
0x05 IFLASH2 FLASH2_EN FLASH2[5:0]
0x06 ITORCH1 TORCH1_EN TORCH1_5:0] TORCH1_
DIM
0x07 ITORCH2 TORCH2_EN TORCH2_5:0] TORCH2_
DIM
0x08 MODE_SEL TORCH_EN_PD FLASH_STB_PD TORCH_MODE[2:0] FLASH_MODE[2:0]
0x09 TX1_MASK TX1_MASK_EN TX1_MASK_PD FLASH_TX1_MASK[5:0]
0x0A TX2_MASK TX2_MASK_EN TX2_MASK_PD FLASH_TX2_MASK[5:0]
0x0B FLASH_
RAMP_SEL FLASH_RU[2:0] FLASH_RD[2:0]
0x0C TORCH_
RAMPSEL TORCH_RU[2:0] TORCH_RD[2:0]
0x0D FLASH_TMR_
CNTL
FLASH_TMR_
CNTL FLASH_TMR[6:0]
0x0E TORCH_
TMR_CNTL
TORCH_TMR_
CNTL TORCH_TMR[4:0]
0x10 MAXFLASH1 MAXFLASH_HYS[2:0] MAXFLASH_TH[4:0]
0x11 MAXFLASH2 LB_TMR_R[3:0] LB_TMR_F[3:0]
0x12 MAXFLASH3 MAX_FLASH1_IMIN[7:0]
0x13 MAXFLASH4 MAX_FLASH2_IMIN[7:0]
0x14 NTC NTC_EN NTC_TH_FLASH[2:0] NTC_TH_TORCH[2:0]
0x15 DCDC_CNTL1 OVP_TH[1:0] FREQ_PWM[1:0] DCDC_MODE[1:0]
0x16 DCDC_CNTL2 DCDC_ADPT_REG[1:0] DCDC_GAIN DCDC_OPERATION[2:0] F_SCALE
[1:0]
0x17 DCDC_ILIM DCDC_ILIM[1:0] DCDC_SS[5:0]
0x18 DCDC_OUT DCDC_OUT[7:0]
0x19 DCDC_OUT_
MAX DCDC_OUT_MAX[7:0]
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
46Maxim Integrated
This register contains manufacture die type information.
This register contains version control.
Table 2. CHIP_ID1
Table 3. CHIP_ID2
Register Name CHIP_ID1
Address 0x00h
Reset Value 0x91
Type Read only
Reset Conditions —
BIT NAME DESCRIPTION DEFAULT VALUE
B7 MSB
DIE_TYPE[7:4] BCD character 9 1001
B6
B5
B4
B3
DIE_TYPE[3:0] BCD character 1 0001
B2
B1
B0 LSB
Register Name CHIP_ID2
Address 0x01h
Reset Value N/A
Type Read only
Reset Conditions —
BIT NAME DESCRIPTION DEFAULT VALUE
B7 MSB
DIE_DASH[3:0] BCD character representing dash number N/A
B6
B5
B4
B3
DIE_REV[3:0] BCD character representing silicon revision N/A
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
47Maxim Integrated
This register contains status of IC.
Table 4. STATUS1
Register Name STATUS1
Address 0x02h
Reset Value 0x00h
Type Read only
Reset Conditions Reset upon read operation and on VDD < VDD_UVLO. Fault
conditions must be cleared before new event can take place.
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB LED1_SHORT
LED1 Current Regulator Output Status
0 = No shorted LED detected.
1 = Shorted LED detected.
0
B6 LED2_SHORT
LED2 Current Regulator Output Status
0 = No shorted LED detected.
1 = Shorted LED detected.
0
B5 REG_IN_UVLO
Indication if REG_IN Input Support is Valid
0 = Valid power at REG_IN.
1 = No valid power at REG_IN.
0
B4 IN_UVLO_THERM
Indication if IN is Valid or Internal Die Temperature is
Fault
0 = Valid power at IN and No temperature fault has occurred.
1 = No valid power at IN or temperature fault has occurred.
0
B3 NTC_THERM
Indication of Status of NTC Resistor
0 = NTC within normal operating range.
1 = NTC over temperature detected.
0
B2 NTC_SHORT
Indication of Status of NTC
0 = NTC not shorted to ground.
1 = NTC shorted to ground detected.
0
B1 OVP_A
Overvoltage Condition Caused by Analog Control Loop
0 = No OVP_A detected.
1 = OVP_A detected.
0
B0 LSB OVP_D
Overvoltage Condition Caused by Digital Control Loop
0 = No OVP_D detected.
1 = OVP_D detected.
0
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
48Maxim Integrated
This register contains status of IC.
Table 5. STATUS2
Register Name STATUS2
Address 0x03h
Reset Value 0x01h
Type Read only
Reset Conditions Reset upon read operation and on VDD < VDD_UVLO or new
flash/torch event triggered.
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB MAXFLASH
Indication of Status of MAXFLASH
0 = MAXFLASH has not occurred during last FLASH event.
1 = MAXFLASH has occurred during last FLASH event.
0
B6 DONE
This is a Simple Indication Where or Not Torch/Flash Event is
Done or Not
0 = Torch/flash event in progress.
1 = Torch/flash event is completed.
0
B5 TX1_MASK
Indication of TX1_MASK
0 = TX1_MASK has not occurred during last FLASH event.
1 = TX1_MASK has occurred during last FLASH event.
0
B4 TX2_MASK
Indication of TX2_MASK
0 = TX2_MASK has not occurred during last FLASH event.
1 = TX2_MASK has occurred during last FLASH event.
0
B3 FLASH_TMR
Indication of Flash Timer
(Only Valid When Operating in Maximum Timer Mode)
0 = Flash timer did not expire during last Flash sequence.
1 = Flash timer expired during last flash sequence.
0
B2 TORCH_TMR
Indication of Torch Timer
(Only Valid When Operating in Maximum Timer Mode)
0 = Torch timer did not expire during last torch sequence.
1 = Torch timer expired during last torch sequence.
0
B1 ILIM
Inductor Current Limit Status
0 = Inductor peak current limit not reached.
1 = Inductor peak current limit reached.
0
B0 LSB nRESET
Indication if Register has been Reset Since Last Operation
0 = I2C registers not reset.
1 = I2C registers reset. Reset upon read.
1
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
49Maxim Integrated
This register contains control output current for flash mode.
Table 6. IFLASH1
Register Name IFLASH1
Address 0x04h
Reset Value 0x29h
Type Read/write
Reset Conditions FLASH1_EN is reset upon UVLO, VDD < VDD_UVLO, or LED1
fault for flash mode.
BIT NAME DESCRIPTION DEFAULT
VALUE
B7
MSB FLASH1_EN
Enable of Flash Mode for FLED1 Current Regulator
0 = FLED1 disabled in flash mode.
1 = FLED1 enabled in flash mode.
0
B6 — — 0
B5
FLASH1[5:0]
Setting Flash Current
000000 = 15.625mA
000001 = 31.25mA
…
111110 = 984.375mA
111111 = 1000mA
101001
B4
B3
B2
B1
B0
LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
50Maxim Integrated
This register contains control output current for flash mode.
Table 7. IFLASH2
Register Name IFLASH2
Address 0x05h
Reset Value 0x29h
Type Read/Write
Reset Conditions FLASH2_EN is reset upon UVLO, VDD < VDD_UVLO, or LED2
fault for flash mode.
BIT NAME DESCRIPTION DEFAULT
VALUE
B7
MSB FLASH2_EN
Enabling Flash Mode for FLED2 Current Regulator
0 = FLED2 disabled in flash mode.
1 = FLED2 enabled in flash mode.
0
B6 — — 0
B5
FLASH2[5:0]
Setting Flash Current
000000 = 15.625mA
000001 = 31.25mA
…
111110 = 984.375mA
111111 = 1000mA
101001
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
51Maxim Integrated
This register contains output current for torch mode.
Table 8. ITORCH1
Register Name ITORCH1
Address 0x06h
Reset Value 0x00h
Type Read/write
Reset Conditions TORCH1_EN is reset upon UVLO, VDD < VDD_UVLO, or LED1
fault for torch mode.
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB TORCH1_EN
Enabling Torch Mode for FLED1 Current Regulator
0 = FLED1 disabled in torch mode.
1 = FLED1 enabled in torch mode.
0
B6
TORCH1[5:0]
Setting TORCH1 Current
DAC Mode
000000 = 3.91mA
000001 = 7.8125mA
…
111110 = 246.1mA
111111 = 250.0mA
PWM Mode
Output current
XXX000 = 125mA duty cycle
XXX001 = 250mA duty cycle
…
XXX110 = 875mA duty cycle
XXX111 = 1000.00mA duty cycle
Duty Cycle
000XXX = 3.125% duty cycle
001XXX = 6.25% duty cycle
…
110XXX = 21.875% duty cycle
111XXX = 25.000% duty cycle
000000
B5
B4
B3
B2
B1
B0 LSB TORCH1_DIM
Select DAC or PWM Dimming for Torch
0 = DAC
1 = PWM
0
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
52Maxim Integrated
This register contains output current for torch mode.
Table 9. ITORCH2
Register Name ITORCH2
Address 0x07h
Reset Value 0x00h
Type Read/write
Reset Conditions TORCH2_EN is reset upon UVLO, VDD < VDD_UVLO, or LED2
fault for torch mode
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB TORCH2_EN
Enabling Torch Mode for FLED2 Current Regulator
0 = FLED2 disabled in torch mode.
1 = FLED2 enabled in torch mode.
1
B6
TORCH2[5:0]
Setting TORCH2 Current
DAC Mode
000000 = 3.91mA
000001 = 7.8125mA
…
111110 = 246.1mA
111111 = 250.0mA
PWM Mode
Output current
XXX000 = 125mA duty cycle
XXX001 = 250mA duty cycle
…
XXX110 = 875mA duty cycle
XXX111 = 1000.00mA duty cycle
Duty Cycle
000XXX = 3.125% duty cycle
001XXX = 6.25% duty cycle
…
110XXX = 21.875% duty cycle
111XXX = 25.000% duty cycle
000000
B5
B4
B3
B2
B1
B0 LSB TORCH2_DIM
Select DAC or PWM Dimming for Torch
0 = DAC
1 = PWM
0
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
53Maxim Integrated
This register control the mode of operation.
Table 10. MODE_SEL
Register Name MODE_SEL
Address 0x08h
Reset Value 0xC0h
Type Read/write
Reset Conditions TORCH_MODE, FLASH_MODE is reset upon UVLO, VDD <
VDD_UVLO, THERM fault, or OVP fault
BIT NAME DESCRIPTION DEFAULT VALUE
B7 MSB TORCH_EN_PD
On/Off Control for Pulldown Resistor of TORCH_EN
Input
0 = Not enabled.
1 = Enabled.
1
B6 FLASH_STB_PD
On/Off Control for Pulldown Resistor of FLASH_STB
Input
0 = Not enabled.
1 = Enabled.
1
B5
TORCH_MODE[2:0]
000 = Torch mode disabled.
001 = Torch mode enabled using TORCH_EN
010 = Torch mode enabled using FLASH_STB
011 = Torch mode enabled using TORCH_EN or
FLASH_STB
100 = Torch mode enabled using TORCH_EN and
FLASH_STB
101 = Torch mode enabled regardless of logic inputs
110 = Torch mode enabled regardless of logic inputs
111 = Torch mode enabled regardless of logic inputs
001B4
B3
B2
FLASH_MODE[2:0]
000 = Flash mode disabled.
001 = Flash mode enabled using TORCH_EN
010 = Flash mode enabled using FLASH_STB
011 = Flash mode enabled using TORCH_EN or
FLASH_STB
100 = Flash mode enabled using TORCH_EN and
FLASH_STB
101 = Flash mode enabled regardless of logic inputs
110 = Flash mode enabled regardless of logic inputs
111 = Flash mode enabled regardless of logic inputs
010B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
54Maxim Integrated
This register contains control output current for flash mode.
Table 11. TX1_MASK
Register Name TX1_MASK
Address 0x09h
Reset Value 0xC0h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB TX1_MASK_EN
On/Off Control for TX1_MASK
0 = Not enabled.
1 = Enabled.
1
B6 TX1_MASK_PD
Enable/Disable Pulldown Resistor for TX1_MASK
0 = Not enabled.
1 = Enabled.
1
B5
FLASH_TX1_MASK[5:0]
Setting Maximum Flash Current During TX1_MASK Event
000000 = 15.625mA
000001 = 31.25mA
…
111110 = 984.375mA
111111 = 1000mA
000000
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
55Maxim Integrated
This register contains control output current for flash mode.
Table 12. TX2_MASK
Register Name TX2_MASK
Address 0x0Ah
Reset Value 0xC0h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7
MSB TX2_MASK_EN
On/Off Control for TX2_MASK
0 = Not enabled.
1 = Enabled.
1
B6 TX2_MASK_PD
Enable/Disable Pulldown Resistor for TX2_MASK
0 = Not enabled.
1 = Enabled.
1
B5
FLASH_TX2_MASK[5:0]
Setting Maximum Flash Current During TX2_MASK Event
000000 = 15.625mA
000001 = 31.25mA
…
111110 = 984.375mA
111111 = 1000mA
000000
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
56Maxim Integrated
This register controls the ramping.
Table 13. FLASH_RAMP_SEL
Register Name FLASH_RAMP_SEL
Address 0x0Bh
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT VALUE
B7 MSB — — 0
B6
FLASH_RU[2:0]
Selection of Flash Ramp-Up Rate
000 = 384Fs
001 = 640Fs
010 = 1152Fs
011 = 2176Fs
100 = 4224Fs
101 = 8.320Fs
110 = 16.512ms
111 = 32.896ms
000
B5
B4
B3 — — 0
B2
FLASH_RD[2:0]
Selection of Flash Ramp-Down Rate
000 = 384Fs
001 = 640Fs
010 = 1152Fs
011 = 2176Fs
100 = 4224Fs
101 = 8.320Fs
110 = 16.512ms
111 = 32.896ms
000
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
57Maxim Integrated
This register controls the ramping.
Table 14. TORCH_RAMP_SEL
Register Name TORCH_RAMP_SEL
Address 0x0Ch
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT VALUE
B7 MSB — 0
B6
TORCH_RU[1:0]
Selection of Torch Ramp-Up Rate
000 = 16.392ms
001 = 32.776ms
010 = 65.544ms
011 = 131.08ms
100 = 262.152ms
101 = 524.296ms
110 = 1.048s
111 = 2.097s
000
B5
B4
B3 — — 0
B2
TORCH_RD[1:0]
Selection of Torch Ramp-Down Rate
000 = 16.392ms
001 = 32.776ms
010 = 65.544ms
011 = 131.08ms
100 = 262.152ms
101 = 524.296ms
110 = 1.048s
111 = 2.097s
000
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
58Maxim Integrated
This register contains control information for flash timer.
Table 15. FLASH_TMR_CNTL
Register Name FLASH_TMR_CNTL
Address 0x0Dh
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB FLASH_TMR_CNTL
Select Timer Mode for Flash Timer
0 = One-shot timer mode
1 = Maximum timer mode
0
B6
FLASH_TMR[6:0]
Selecting for Flash Timer
0000000 = 0.128ms
0000001 = 0.384ms
0000010 = 0.640ms
0000011 = 0.896ms
0000100 = 1.41ms
0000101 = 1.92ms
0000101 = 1.92ms
0001110 = 2.43ms
0000111 = 2.94ms
0001000 = 3.97ms
0001001 = 4.99ms
… (1.024ms step size)
0001110 = 10.11ms
0001111 = 11.14ms
0010000 = 13.18ms
0010001 = 15.23ms
… (2.048ms step size)
0011110 = 41.86ms
0011111 = 43.90ms
0100000 = 48.00ms
0100001 = 52.09ms
… (4.096ms step size)
0111110 = 170.88ms
0111111 = 174.98ms
1000000 = 183.17ms
1000001 = 191.36ms
… (8.192ms step size)
1111110 = 691.07ms
1111111 = 699.26ms
0000000
B5
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
59Maxim Integrated
This register contains control information for torch timer.
Table 16. TORCH_TMR_CNTL
Register Name TORCH_TMR_CNTL
Address 0x0Eh
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB TORCH_TMR_CNTL
Select Timer Mode for Torch Timer
0 = One-shot timer mode.
1 = Timer mode disabled.
0
B6
TORCH_TMR[4:0]
Selecting for Torch Timer
00000 = 122.88ms
… (131.072ms step size)
00011 = 516.096ms
… (262.144 step size)
00100 = 778.24ms
00111 = 1564.67ms
… (262.144 step size)
01000 = 2088.96ms
01111 = 5758.976ms
… (524.288ms step size)
10000 = 6807.552ms
11110 = 21487.616ms
11111 = 22536.192ms
… (1048.576ms step size)
00000
B5
B4
B3
B2
B1 — — 0
B0 LSB — — 0
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
60Maxim Integrated
This register contains control information for MAXFLASH.
Table 17. MAXFLASH1
Register Name MAXFLASH1
Address 0x10h
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
MAXFLASH_HYS[2:0]
Selects Hysteresis for MAXFLASH
000 = Off, LED current only allowed to decrease
001 = 50mV
010 = 100mV
110 = 300mV
111 = 350mV
000
B6
B5
B4
MAXFLASH_TH[4:0]
Selects MAXFLASH Threshold
00000 = Off, MAXFLASH disabled.
00001 = 2.40V
00010 = 2.433V
…
11110 = 3.366V
11111 = 3.40V
000000
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
61Maxim Integrated
This register contains control information for MAXFLASH.
Table 18. MAXFLASH2
Register Name MAXFLASH2
Address 0x11h
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
LB_TMR_R[3:0]
Selects MAXFLASH Timer for Rising Input Voltage
0000 = 256Fs
0001 = 512Fs
…
1110 = 1792Fs
1111 = 2048Fs
0000
B6
B5
B4
B3
LB_TMR_F[3:0]
Selects MAXFLASH Timer for Falling Input Voltage
0000 = 256Fs
0001 = 512Fs
…
1110 = 1792Fs
1111 = 2048Fs
0000
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
62Maxim Integrated
This register contains control information for MAXFLASH.
This register contains control information for MAXFLASH
Table 19. MAXFLASH3
Table 20. MAXFLASH4
Register Name MAXFLASH3
Address 0x12h
Reset Value 0x3Fh
Type Read only
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
MAX_FLASH1_IMIN[7:0] Minimum output current logged for LED (FLED1) during a
MAXFLASH event 00111111
B6
B5
B4
B3
B2
B1
B0 LSB
Register Name MAXFLASH4
Address 0x13h
Reset Value 0x3Fh
Type Read only
Reset Conditions —
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
MAX_FLASH2_IMIN[7:0] Minimum output current logged for LED (FLED2) during a
MAXFLASH event 00111111
B6
B5
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
63Maxim Integrated
This register contains control information for NTC function.
Table 21. NTC
Register Name NTC
Address 0x14h
Reset Value 0x00h
Type Read/Write
Reset Conditions NTC_EN bit is cleared on NTC_SHORT detected. Reset upon
VDD < VDD_UVLO.
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB NTC_EN
On/Off Control of NTC Input
0 = Disabled.
1 = Enabled.
0
B6
NTC_TH_FLASH[2:0]
Selects Threshold for Hot for Flash Mode
000 = 200mV
001 = 250mV
…
110 = 500mV
111 = 550mV
000
B5
B4
B3
NTC_TH_TORCH[2:0]
Selects Threshold for Hot for Torch Mode
000 = 200mV
001 = 250mV
…
110 = 500mV
111 = 550mV
000
B2
B1
B0 LSB 0
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
64Maxim Integrated
This register contains control information for DC-DC converter.
Table 22. DCDC_CNTL1
Register Name DCDC_CNTL1
Address 0x15h
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
OVP_TH[1:0]
Selects Overvoltage Threshold for the DC-DC Converter
Output Voltage
00 = 4.50V
01 = 4.80V
10 = 5.10V
11 = 5.40V
00
B6
B5 — — 0
B4 — — 0
B3
FREQ_PWM[1:0]
Selection of Frequency for PWM of Current Regulators
00 = 7.8kHz
01 = 1.9kHz
10 = 488Hz
11 = 122Hz
00
B2
B1
DCDC_MODE
00 = Adaptive mode. DCDC is enabled together with current
regulators.
01 = Prebiased adaptive mode. Output is prebiased and DC-DC is
enabled together with current regulators.
10 = Forced active mode with output regulating at DCDC_SS.
11 = Dropout mode.
00
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
65Maxim Integrated
This register contains control information for DC-DC converter.
Table 23. DCDC_CNTL2
Register Name DCDC_CNTL2
Address 0x16h
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7
MSB
DCDC_ADPT_REG[1:0]
Sets the Adaptive Regulation Threshold for the DC-DC Converter
00 = 120mV
01 = 150mV
10 = 180mV
11 = 210mV
00
B6
B5 DCDC_GAIN 0 = Standard
1 = Enhancement 0
B4
DCDC_OPERATION[2:0]
Mode for DC-DC Converter
000
B4, B3, B2 Mode Frequency DC Min (%)
B3
000 SKIP 1MHz Fixed 3.125
001 SKIP 4MHz Auto
Adjust 3.125
010 FPWM 4MHz Fixed 12.50
011 FPWM 4MHz Auto
Adjust 3.125
B2
100 FPWM 1MHz Fixed 3.125
101 FPWM 2MHz Fixed 12.50
110 FPWM 2MHz Auto
Adjust 3.125
111 SKIP 2MHz Auto
Adjust 3.125
B1
— — 00
B0
LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
66Maxim Integrated
This register contains control information for DC-DC converter.
Table 24. DCDC_LIM
Register Name DCDC_LIM
Address 0x17h
Reset Value 0x00h
Type Read/write
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
DCDC_ILIM[1:0]
Selects Current Limit for Low-Side Switch (per phase)
00 = 1.25
01 = 1.5
10 = 1.75
11 = 2.0
00
B6
B5
DCDC_SS[5:0]
Set the Soft-Start Threshold for the DC-DC Converter
000000 = 2.3V
000001 = 2.35V
…
111110 = 5.15V
111111 = 5.2V
000000
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
67Maxim Integrated
This register contains control information about the actual regulation threshold for the DCD converter during adaptive
regulation.
Table 25. DCDC_OUT
Register Name DCDC_OUT
Address 0x18h
Reset Value 0x00h
Type Read only
Reset Conditions Reset upon VDD < VDD_UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
DCDC_OUT[7:0]
Readback Information Regarding Adaptive Regulation Output
Voltage
00000000 = 2.3V
00000001 = 2.3125V
…
11111110 = 5.1875V
11111111 = 5.2V
00000000
B6
B5
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
68Maxim Integrated
This register contains control information about the maximum regulation threshold for the DCD converter during adap-
tive regulation.
Table 26. DCDC_OUT_MAX
Register Name DCDC_OUT_MAX
Address 0x19h
Reset Value 0x00h
Type Read only
Reset Conditions Reset upon triggering torch or flash mode and VDD < VDD_
UVLO
BIT NAME DESCRIPTION DEFAULT
VALUE
B7 MSB
DCDC_OUT_MAX[7:0]
Readback Information Regarding Adaptive Regulation Output
Voltage
00000000 = 2.3V
00000001 = 2.3125V
…
11111110 = 5.1875V
11111111 = 5.2V
00000000
B6
B5
B4
B3
B2
B1
B0 LSB
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
69Maxim Integrated
Applications Information
Programming the I2C Registers
It is critical to program the IC in the correct sequence to
ensure proper operation.
Changing any register values other than the DCDC_
MODE bits in the DCDC_CNTL1 register during a flash
or torch event is not advised. Poll the STATUS2 register
to wait for the DONE bit to be asserted before changing
values.
Sequencing can be divided in to three groups flash and
torch mode and DC-DC output voltage.
For flash mode, the following sequence is recommended:
1. Clear any pending fault status by reading the STATUS1
register. Failing to do this can result in incorrect values
written is some of the registers. For example, failing to
clear a FLED1 or FLED2 fault clears the FLED1_EN or
FLED2_EN, respectively, disabling the current regula-
tors remain disabled until the FLED_ fault is cleared in
the STATUS1 register.
2. Ensure that flash mode is not enabled, by setting the
FLASH_MODE bits to 000 in the MODE_SEL register.
Ensure the DCDC_MODE bits are 00 in the DCDC_
CNTL1 register.
3. If the TX_MASK function is required for flash opera-
tion, write the appropriate values into the TX1_MASK
and TX2_MASK register. This register does not need
to be updated if current values are already set.
4. Select the ramp rate in the FLASH_RAMP_SEL reg-
ister for ramping up/down the FLED current. These
registers do not need to be updated if current values
are already set.
5. Select the flash timer and mode of operation by writ-
ing to the FLASH_TMR_CNTL register. This register
does not need to be updated if current values are
already set.
6. If the MAXFLASH function is required for flash opera-
tion, write the appropriate values into the MAXFLASH1
and MAXFLASH2 registers. These registers do not
need to be updated if current values are already set.
7. If the NTC function is required for flash operation,
write the appropriate values into the NTC register.
This register does not have to be updated if current
values are already set.
8. Select the settings for the DC-DC converter by writ-
ing to the DCDC_CNTL2 and DCDC_ILIM registers.
These registers do not need to be updated if current
values are already set.
9. Select the settings for the flash mode by writing to the
FLASH1 and FLASH2 registers. These registers do
not need to be updated if current values are already
set.
10. Select the settings for the DCDC_CNTL1 register.
11. Select the trigger mode for flash event by writing to
the FLASH_MODE bits in the MODE_SEL register.
This register does not need to be updated if current
values are already set.
Now the flash event is ready to be triggered based on the
value set for the FLASH_MODE setting.
For hardware triggering, set FLASH_MODE = 001, 010,
011, or 100. Flash event is retriggered based on logic
input. No update to I2C registers is required.
For software triggering, set FLASH_MODE = 101, 110,
or 111. Flash event is triggered once FLASH_MODE
changes from an external trigger to a software trigger. If
an additional flash event is required through a software
trigger, the FLASH_MODE needs to be set to 000 first
before writing to the software value (101, 110, or 111) to
retrigger a new flash event.
For torch mode, the following sequence is recommended:
1. Clear any pending fault status by reading the STATUS1
register. Failing to do this can result in incorrect values
written to some of the registers. For example, failing
to clear a FLED1 or FLED2 fault clears the FLED1_EN
or FLED2_EN, respectively, disabling the current
regulators that remain disabled until the FLED_ fault
is cleared in the STATUS1 register. When the FLED_
fault is cleared, the TORCH_EN can be set.
2. Ensure that torch mode is not enabled by setting the
TORCH_MODE to 000 in the MODE_SEL register.
Ensure the DCDC_MODE bits are 00 in the DCDC_
CNTL1 register.
3. Select the ramp rate in the TORCH_RAMP_SEL regis-
ter for ramping up/down the torch FLED current. This
register does not need to be updated if current values
are already set.
4. Select the torch timer and mode of operation by writ-
ing to the TORCH_TMR_CNTL register. This register
does not need to be updated if current values are
already set.
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
70Maxim Integrated
5. If the MAXFLASH function is required for torch opera-
tion, write the appropriate values into the MAXFLASH1
and MAXFLASH2 registers. These registers do not
need to be updated if current values are already set.
6. If the NTC function is required for torch operation,
write the appropriate values into the NTC register.
This register does not need to be updated if current
values are already set.
7. Select the settings for the DC-DC converter by writ-
ing to the DCDC_CNTL2 and DCDC_ILIM registers.
These registers do not need to be updated if current
values are already set.
8. Select the settings for the torch mode by writing to the
TORCH1 and TORCH2 registers. These registers do
not need to be updated if current values are already
set.
9. Select the settings for the DCDC_CNTL1 register.
10. Select the trigger mode for the torch event by writing
to the TORCH_MODE bits in the MODE_SEL register.
This register does not need to be updated if current
values are already set.
Now the torch event is ready to be triggered based on
the value set for the TORCH_MODE setting.
For hardware triggering set TORCH_MODE = 001, 010,
011, or 100. A torch event is retriggered based on logic
input. No update to I2C registers is required.
For software triggering, set TORCH_MODE = 101, 110,
or 111. A torch event is triggered once TORCH_MODE
changes from an external trigger to a software trigger. If
an additional torch event is required through a software
trigger, the TORCH_MODE needs to be set to 000 first
before writing to the software value (101, 110, or 111) to
retrigger a new torch event.
For DC-DC fixed voltage mode and dropout output volt-
age, the following sequence is recommended:
1. Clear any pending fault status by reading the STATUS1
register. Failing to do this can result in incorrect val-
ues written is some of the registers.
2. Ensure the DCDC_MODE bits are 00 in the DCDC_
CNTL1 register.
3. For fixed output voltage mode, select the settings for
the DC-DC converter by writing to the DCDC_CNTL2
and DCDC_ILIM registers. These registers do not have
to be updated if current values are already set.
4. Select the settings for DCDC_CNTL1 register includ-
ing the DCDC_MODE bits. Writing anything other
than 00 to the DCDC_MODE bits enables the DC-DC
converter.
During a torch or flash event, the following optional reg-
isters can be read:
The DCDC_OUT register contains current information
regarding the output voltage settings. The actual output
voltage is slightly lower due to the load regulation of the
DC-DC converter. It is not required to read this register
during a torch or flash event.
STATUS1 register contains current information if any
fault condition occurs during the torch or flash event. It is
optional to read this register during torch or flash event.
The STATUS2 register contains information regarding
any events that might have happened during a torch or
flash event.
After a torch or flash event the following optional register
can be read:
The DCDC_OUT_MAX register contains the last adap-
tive output voltage to which the converter has regulated
the output. This information can be used to adjust the
DCDC_SS setting.
The STATUS1 register contains information regarding
any fault condition that might have occurred during a
torch or flash event.
The STATUS2 register contains information regarding
any events that might have happened during a torch or
flash event.
If the MAXFLASH is enabled, the MAXFLASH3 and
MAXFLASH4 registers contain the minimum current set-
ting that the current regulators where regulating to during
the MAXFLASH event. The STATUS2 register contains a
MAXFLASH bit indicating if the MAXFLASH was active
during the torch or flash event.
It should be note that during fixed output voltage mode,
the output is regulated to the DCDC_SS value that was
set during the enabling of the converter. The DCDC_SS
value can be updated when the converter is enabled, but
this does not impact the output voltage.
To change the output voltage, first power down the DC-DC
converter (DCD_MODE = 00), then update the DCDC_SS
value, and then power it up again (DCDC_MODE = 10).
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
71Maxim Integrated
Output Voltage Operating Range
The capability of the DC-DC converter of the IC is
depending on following parameters:
U Input voltage
U Output voltage
U Efficiency for given range of operation
U Inductor value
U Switching frequency
U Peak input current limit of the IC
The following tables give examples of different operating
conditions with the respective input and output voltage
limitations.
Note: For fSW = 4MHz, L = 0.5µH.
Table 27. Maximum Output Voltage for 2A Output Current as a Function of VIN
and IPEAK
IPEAK (PER PHASE)
1.25A 1.50A 1.75A 2.00A
VIN VOUT max support for 2A output current
2.50V 2.50V 2.69V 3.19V 3.69V
2.60V 2.60V 2.82V 3.34V 3.87V
2.70V 2.70V 2.95V 3.50V 4.05V
2.80V 2.80V 3.08V 3.66V 4.24V
2.90V 2.90V 3.21V 3.82V 4.43V
3.00V 3.00V 3.35V 3.98V 4.62V
3.10V 3.10V 3.48V 4.15V 4.82V
3.20V 3.20V 3.62V 4.32V 5.00V
3.30V 3.30V 3.76V 4.48V 5.00V
3.40V 3.40V 3.90V 4.65V 5.00V
3.50V 3.50V 4.04V 4.82V 5.00V
3.60V 3.60V 4.13V 4.94V 5.00V
3.70V 3.70V 4.22V 5.00V 5.00V
3.80V 3.80V 4.32V 5.00V 5.00V
3.90V 3.90V 4.41V 5.00V 5.00V
4.00V 4.00V 4.50V 5.00V 5.00V
4.10V 4.10V 4.59V 5.00V 5.00V
4.20V 4.20V 4.68V 5.00V 5.00V
4.30V 4.30V 4.76V 5.00V 5.00V
4.40V 4.40V 4.85V 5.00V 5.00V
4.50V 4.50V 4.94V 5.00V 5.00V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
72Maxim Integrated
Note: For fSW = 4MHz, L = 0.5µH.
Table 28. Maximum Output Voltage for 1.5A Output Current as a Function of VIN
and IPEAK
IPEAK (PER PHASE)
1.25A 1.50A 1.75A 2.00A
VIN VOUT max support for 1.5A output current
2.50V 2.92V 3.58V 4.25V 4.92V
2.60V 3.05V 3.76V 4.46V 5.00V
2.70V 3.19V 3.93V 4.67V 5.00V
2.80V 3.33V 4.11V 4.88V 5.00V
2.90V 3.47V 4.28V 5.00V 5.00V
3.00V 3.61V 4.46V 5.00V 5.00V
3.10V 3.75V 4.64V 5.00V 5.00V
3.20V 3.90V 4.83V 5.00V 5.00V
3.30V 4.04V 5.00V 5.00V 5.00V
3.40V 4.19V 5.00V 5.00V 5.00V
3.50V 4.33V 5.00V 5.00V 5.00V
3.60V 4.43V 5.00V 5.00V 5.00V
3.70V 4.52V 5.00V 5.00V 5.00V
3.80V 4.62V 5.00V 5.00V 5.00V
3.90V 4.71V 5.00V 5.00V 5.00V
4.00V 4.80V 5.00V 5.00V 5.00V
4.10V 4.89V 5.00V 5.00V 5.00V
4.20V 4.98V 5.00V 5.00V 5.00V
4.30V 5.00V 5.00V 5.00V 5.00V
4.40V 5.00V 5.00V 5.00V 5.00V
4.50V 5.00V 5.00V 5.00V 5.00V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
73Maxim Integrated
Note: For fSW = 4MHz, L = 0.5µH.
For conditions other than those specified in the tables above the maximum output voltage that can be supported by the
IC can be calculated using following formula:
IN(MIN)
PEAK IN(MIN)
SW
OUT OUT(MAX)
V
2I V
2Lf
VI
− η×
××
=
VOUT cannot exceed OVP_D minus load regulation.
Table 29. Maximum Output Voltage for 1.0A Output Current as a Function of VIN
and IPEAK
IPEAK (PER PHASE)
1.25A 1.50A 1.75A 2.00A
VIN VOUT max support for 1.0A output current
2.50V 4.38V 5.00V 5.00V 5.00V
2.60V 4.58V 5.00V 5.00V 5.00V
2.70V 4.79V 5.00V 5.00V 5.00V
2.80V 5.00V 5.00V 5.00V 5.00V
2.90V 5.00V 5.00V 5.00V 5.00V
3.00V 5.00V 5.00V 5.00V 5.00V
3.10V 5.00V 5.00V 5.00V 5.00V
3.20V 5.00V 5.00V 5.00V 5.00V
3.30V 5.00V 5.00V 5.00V 5.00V
3.40V 5.00V 5.00V 5.00V 5.00V
3.50V 5.00V 5.00V 5.00V 5.00V
3.60V 5.00V 5.00V 5.00V 5.00V
3.70V 5.00V 5.00V 5.00V 5.00V
3.80V 5.00V 5.00V 5.00V 5.00V
3.90V 5.00V 5.00V 5.00V 5.00V
4.00V 5.00V 5.00V 5.00V 5.00V
4.10V 5.00V 5.00V 5.00V 5.00V
4.20V 5.00V 5.00V 5.00V 5.00V
4.30V 5.00V 5.00V 5.00V 5.00V
4.40V 5.00V 5.00V 5.00V 5.00V
4.50V 5.00V 5.00V 5.00V 5.00V
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
74Maxim Integrated
Inductor Selection
The IC is designed to use a 0.47FH to 1.0FH inductor per
phase. Selecting a higher inductance value increases
efficiency by reducing inductor peak-to-peak current with
the trade-off in solution size.
To prevent core saturation, ensure that the inductor-sat-
uration current rating exceeds the peak inductor current
for the application. Calculate the worst-case peak induc-
tor current with the following formula:
OUT OUT(MAX) IN(MIN)
PEAK IN(MIN) SW
VI V
I2 V 2Lf
×
= +
×η× × ×
where:
L is the inductance chosen.
fSW is the actual switching frequency for the IC.
E is the DC-DC converter efficiency. See the appropriate
typical operating curve.
Table 30. Suggested Inductors
MANUFACTURER SERIES INDUCTANCE (µH) DCR
(mI)
ISAT
(A)
DIMENSIONS
(LTYP x WTYP x HMAX) (mm)
RECOMMENDED INDUCTORS FOR THE ILIM 1.25A SETTING
Coilcraft
PFL1610 0.47 85 1.8 1.8 x 1.0 x 1.0
XPL2010
0.50
0.68
0.82
1.00
40
57
68
89
2.35
1.95
1.65
1.60
2.0 x 1.9 x 1.0
SEMCO CIG21LR47MNE 0.47 96 1.35 2.0 x 1.25 x 1.0
CIG22L1R0MNE 1.0 60 1.6 2.5 x 2.0 x 1.0
TOKO MDT2012-CR 0.56 65 1.5 2.0 x 1.25 x 1.0
TDK VLS2012 0.47 54 1.85 2.0 x 1.6 x 0.95
0.68 72 1.65
Cyntec
PSB1210T 0.33 68 2.1 1.25 x 1.0 x 1.0
0.5 85 1.48
PIFE20161B 0.47
1.0
30
60
3.6
2.4 2.0 x 1.6 x 1.2
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
75Maxim Integrated
Table 30. Suggested Inductors (continued)
MANUFACTURER SERIES INDUCTANCE (µH) DCR
(mI)
ISAT
(A)
DIMENSIONS
(LTYP x WTYP x HMAX) (mm)
RECOMMENDED INDUCTORS FOR THE ILIM 1.5A SETTING
Coilcraft
PFL1610 0.47 85 1.8 1.8 x 1.0 x 1.0
XPL2010 0.50
0.68
40
57
2.35
1.95 2.0 x 1.9 x 1.0
TOKO MDT2012-CR 0.56 65 1.5 2.0 x 1.25 x 1.0
DEM2812C 1.0 66 1.6 3.2 x 3.0 x 1.2
SEMCO CIG2MWR47MNE 0.47 75 1.8 2.0 x 1.25 x 1.0
TDK VLS2012 0.47 54 1.85 2.0 x 1.6 x 0.95
0.68 72 1.65
Cyntec
PSI2520 0.47 40 2.3 2.5 x 2.0 x 1.0
PIFE2520T 0.47
1.0
34
54
4.5
3.5 2.5 x 2.0 x 1.0
PIFE20161B 0.47
1.0
30
60
3.6
2.4 2.0 x 1.6 x 1.2
PSB1210T 0.33 68 2.1 1.25 x 1.0 x 1.0
RECOMMENDED INDUCTORS FOR THE ILIM 1.75A SETTING
Coilcraft PFL2010 0.47 60 1.8 2.0 x 1.46 x 1.0
XPL2010 0.50 40 2.35 2.0 x 1.9 x 1.0
TDK VLS2012 0.47 54 1.85 2. 0x 1.6 x 0.95
SEMCO CIG22HR47 0.47 52 3.8 2.5 x 2.0 x 1.0
Cyntec
PSI2520 0.47 40 2.3 2.5 x 2.0 x 1.0
PSB1210T 0.33 68 2.1 2.5 x 2.0 x 1.0
PIFE2520T 0.47
1.0
34
54
4.5
3.5 2.5 x 2.0 x 1.0
PIFE20161B 0.47
1.0
30
60
3.6
2.4 2.0 x 1.6 x 1.2
RECOMMENDED INDUCTORS FOR THE ILIM 2.0A SETTING
CoilCraft XPL2010 0.50 40 2.35 2.0 x 1.9 x 1.0
SEMCO CIG22HR47 0.47 52 3.8 2.5 x 2.0 x 1.0
TDK VLF3025 1.0 33 2.0 3.0 x 2.5 x 1.0
Cyntec
PSI2520 0.47 40 2.3 2.5 x 2.0 x 1.0
PSB1210T 0.33 68 2.1 1.25 x 1.0 x 1.0
PIFE2520T 0.47
1.0
34
54
4.5
3.5 2.5 x 2.0 x 1.0
PIFE20161B 0.47
1.0
30
60
3.6
2.4 2.0 x 1.6 x 1.2
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
76Maxim Integrated
Input Capacitor Selection
The input capacitor required consists of two capacitors.
One capacitor is used for decoupling the input to IN.
The other is for decoupling the inductors to reduce input
ripple.
The IN should be decoupled using a minimum capaci-
tance of 0.08FF. This capacitor is required to ensure a
low noise input to IN and is critical for MAXFLASH and
adaptive regulation quality.
The input capacitor for the inductor is required to support
the ripple current from the DC-DC converter switching.
The input capacitor needs to have a minimum capaci-
tance of 4FF. Ensure that with voltage derating that the
value of the capacitor is sufficient to ensure stability of
the converter. Since capacitors can derate as much as
40% to 60%, a 10FF capacitor is recommended. See
Table 31 below for recommended capacitors.
Another critical parameter for the input capacitor is that
the impedance at 8MHz is as low as possible. Since the
ripple frequency of the converter is 2x 4MHZ, choosing
an input capacitor with high impedance at this frequency
results in increased input ripple, reducing the perfor-
mance of the IC.
Output Capacitor Selection
The output capacitor is one of the critical items in deter-
mining the output ripple current of the FLED output. The
current regulator output ripple current is generated from
the voltage ripple existing on the OUT capacitor due to
DC-DC step up converter switching.
The voltage ripple on OUT capacitor is mainly due to the
following two factors:
ESR of the output capacitor.
DV across the output capacitor caused by the charge
and discharge cycle.
Therefore, the choice of output capacitor has a large
impact on the output ripple of the current regulators. In
order to ensure low output ripple current, the following
steps should be taken:
1. Select an output capacitor with a low ESR.
2. Select an output capacitor with low impedance at the
switching frequency.
3. In the PCB layout careful routing between the IC
and output capacitors can reduce ripple current. By
routing to the output capacitor as a star connection
the ripple that is injected into the current regulator is
reduced by ILX_xRTRACE1. Even though this is a small
reduction in ripple, it still aids in producing a low out-
put ripple current.
4. (Optional) A capacitor at REG_IN can even further
reduce the output ripple current. The additional
capacitor at REG_IN reduces the overall ESR of the
output capacitor by having more capacitors in paral-
lel. Also the connection between the output capacitor
and the capacitor at REG_IN acts at a high-frequency
filter since the trace acts like an inductor forming a
LC filter. This is especial effective in filtering away the
switching edges of the DC-DC converter.
Table 31. Suggested Input Capacitors
Figure 19. Output Capacitor Start Connection
MANUFACTURER SERIES CAPACITANCE (µF) ESR
(mI at 4HMz)
DIMENSIONS
(LTYP x WTYP x HMAX) (mm)
Samsung CL05A106MP5NUNC 10 9 1.0 x 0.5 x 0.5
Murata GRM188R60J106ME84 10 10 1.6 x 0.6 x 0.085
Samsung CL05A104KA5NNNC 0.1 4.6 1.0 x 0.5 x 0.5
Taiyo Yuden TMK105BJ1040KV 0.1 20 1.0 x 0.5 x 0.5
Murata GRM155R61E104KA87 0.1 15 1.0 x 0.5 x 0.5
ESR
REG_IN
RTRACE2
RTRACE1
RTRACE3
ESR
OUT_B
OUT_A
Figure 19
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
77Maxim Integrated
Chip Information
PROCESS: BiCMOS
The output capacitors needs to have a minimum capaci-
tance of 6FF for DCDC_GAIN = 0 and a minimum capaci-
tance of 12FF for DCDC_GAIN = 1 and operating in non
adaptive mode. Ensure that with voltage derating that
the value of the capacitor is sufficient to ensure stability
of the converter. Since capacitors can derate as much
as 40% to 60%, a 10FF capacitor for each output is rec-
ommended for DCDC_GAIN of 0. With DCDC_GAIN of
1 either a 20FF capacitor or 2x 10FF capacitors at each
output is recommended.
An optional capacitor at REG_IN of 4.7FF can help
increase the performance of the current regulator.
See Table 32 for recommended capacitors.
PCB Layout
Layout is critical for the performance of the IC. Proper
layout ensures good thermal conditions for the IC as
well as minimizing EMI disturbances and most important
good current sharing between the two phases.
Bypass IN to AGND with a ceramic capacitor. Ceramic
capacitors with X5R and X7R dielectrics are recommend-
ed for their low ESR and tighter tolerances over a wide
temperature ranges. Place the capacitor as close as pos-
sible to the IN input bump with a value recommended in
the input capacitor selection section. Place an additional
capacitor from IN to PGND,close to the inductor (shared
for both phases) with a recommended value give in the
input capacitor selection section.
Bypass OUT_ to PGND_ with a ceramic capacitor.
Ceramic capacitors with X5R and X7R dielectrics are
recommended for their low ESR and tighter tolerances
over a wide temperature ranges. Place the capacitor
as close as possible to the IC. Ensure that the rout-
ing form IC to output capacitor is as identical for each
phase as possible since this yields the best efficiency.
The minimum required output capacitor value is given in
output capacitor selection section. Ensure that OUT_A
and OUT_B are routed directly to the output capacitor
before routed to REG_IN. Doing this minimizes the out-
put ripple current on the LED due to voltage ripple on
the output capacitor. For enhanced performance of the
current regulator, an additional capacitor can be paced
at REG_IN_. This reduces the output ripple current of the
current regulator and overall enhances the performance
of the current regulator.
Keep the ground loop among the input, output and the IC
as short as possible since this ground plane is carrying
the full load current.
Keep the connection between the LX_ and inductor as
short as possible. Keep the LX_ trace away from noise
sensitive traces.
Ensure that the layout for each of the phases is as sym-
metrical as possible since this yields the best current
sharing between the two phases.
The trace from FLED_ to the anode of the FLED_ can be
longer, but keeping this trace low impedance is critical
for the efficiency of the applications as well as getting
heat transferred away from the IC.
Place as much ground as possible around the IC since
this enhances the thermal properties of the device.
Table 32. Suggested Output Capacitors
MANUFACTURER SERIES CAPACITANCE (µF) ESR
(mI at 4HMz)
DIMENSIONS
(LTYP x WTYP x HMAX = VOLUME) (mm)
Samsung CL05A106MP5NUNC 10 9 1.0 x 0.5 x 0.5
Murata GRM188R60J106ME84 10 10 1.6 x 0.6 x 0.085
Samsung CL05A475KP5NRNC 4.7 5 1.0 x 0.5 x 0.5
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
78Maxim Integrated
Figure 20. 20-Bump WLP Recommended Layout for 2x1.5A Input Current Limit
Cout
CIN
Cout
CDD
LX_A
OUT_A TX1_
MASK
TX2_
MASK
PGND_B
VDD SCL
SDAFLED
PGND_A TORCH_
EN
FLASH_
STB
NTC
FLED
Cut
CIN
Cout
C
OUT
LX_B
OUT_B
IN
AGND
Cout
COUT
REG_IN
REG_INI
L
MDT2012
1.0mm HEIGHT
L
MDT2012
1.0mm HEIGHT
3.0mm
4.15mm
Figure 20
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
79Maxim Integrated
Simplified Block Diagram
Ordering Information Package Information
For the latest package outline information and land patterns (foot-
prints), go to www.maximintegrated.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but the
drawing pertains to the package regardless of RoHS status.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
PART TEMP RANGE PIN-PACKAGE
MAX77387EWP+T -40NC to +85NC20 WLP
MAX77387EWP+ -40NC to +85NC20 WLP
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND PATTERN
NO.
20 WLP W201D2+1 21-0544
Refer to
Application
Note 1891
MAX77387
LX_A
PGND_A
PGND_B
LX_B
IN
AGND
VDD
SDA
REGISTERS
AND
CONTOL
LOGIC
OUT_A
OUT_B
REGIN
FLED1
FLED2
BATTERY
2.5V TO 5.5V
0.47µH
0.47µH
UVLO AND
MAXFLASH
SCL
TX1_MASK
TX2_MASK
TORCH_EN
FLASH_STB
NTC
4MHz
DC-DC
STEP UP
CONVERTER
4MHz
DC-DC
STEP UP
CONVERTER
MAX77387
Dual-Phase Adaptive DC-DC Step-Up Converter
With 2x 1000mA High-Side Current Regulators
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent
licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max
limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000 80
© 2012 Maxim Integrated Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
Revision History
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NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 7/12 Initial release —
