LM3554TME - Texas Instruments High-Performance Analog

LM3554

LM3554 Synchronous Boost Converter with 1.2A Dual High Side LED Drivers

and I 2 C-Compatible Interface

Literature Number: SNVS549A

LM3554

April 12, 2011

Synchronous Boost Converter with 1.2A Dual High Side

LED Drivers and I2C-Compatible Interface

General Description

The LM3554 is a 2MHz fixed frequency, current mode syn-

chronous boost converter. The device is designed to operate

as a dual 600mA (1.2A total) constant-current driver for high-

current white LEDs, or as a regulated 4.5V or 5V voltage

source.

The dual high-side current sources allow for grounded cath-

ode LED operation. An adaptive regulation method ensures

the current source for each LED remains in regulation and

maximizes efficiency.

The main features include: an I2C-compatible interface for

controlling the LED current or the desired output voltage, a

hardware Flash enable input for direct triggering of the Flash

pulse, and dual TX inputs which force the Flash pulse into a

low-current Torch mode allowing for synchronization to RF

power amplifier events or other high-current conditions. Ad-

ditionally, an active high hardware enable (HWEN) input pro-

vides a hardware shutdown during system software failures.

Five protection features are available within the LM3554 in-

cluding a software selectable input voltage monitor, an inter-

nal comparator for interfacing with an external temperature

sensor, four selectable current limits to ensure the battery

current is kept below a predetermined peak level, an over-

voltage protection feature to limit the output voltage during

LED open circuits, and an output short circuit protection which

limits the output current during shorts to GND. Additionally,

the device provides various fault indicators including: a ther-

mal fault flag indicating the LED temperature has tripped the

thermal threshold, a flag indicating a TX event has occurred,

a flag indicating the flash timeout counter has expired, a flag

indicating the devices die temperature has reached the ther-

mal shutdown threshold, and a flag indicating an open or short

LED.

Features

■Dual High Side Current Sources

■Grounded Cathode Allowing for Better Heat Sinking and

LED Routing

■>90% Efficiency

■Ultra-Small Solution Size: < 23mm2

■Four Operating Modes: Torch, Flash, LED Indicator and

Voltage Output

■Accurate and Programmable LED Current from 37.5mA to

1.2A

■Programmable 4.5V or 5.0V Constant Output Voltage

■Hardware Flash and Torch Enable

■LED Thermal Sensing and Current Scaleback

■Software Selectable Input Voltage Monitor

■Programmable Flash Timeout

■Dual Synchronization Inputs for RF Power Amplifier Pulse

Events

■Open and Short LED Detection

■Active High Hardware Enable for Protection Against

System Faults

■400kHz I2C-Compatible Interface

■16-Bump (1.7mm × 1.7mm × 0.6mm) micro SMD

Applications

■Camera Phone LED Flash Controller

■Class D Audio Amplifier Power

■LED Current Source Biasing

Typical Application Circuits

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Example Layout

Synchronous Boost Converter with 1.2A Dual High Side LED Driver and I2C-Compatible Interface

Application Circuit Component List

Component Manufacturer Value Part Number Size (mm) Rating

L TOKO 2.2µH FDSE0312-2R2M 3×3×1.2 2.3A(0.2Ω)

COUT Murata 4.7µF/10µF GRM188R60J475M, or

GRM188R60J106M

1.6×0.8×0.8 (0603) 6.3V

CIN Murata 4.7µF GRM185R60J475M 1.6×0.8×0.8 (0603) 6.3V

LEDs Lumiled LXCL-PWF4 1.5A

Connection Diagram

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Pin Descriptions

Pin Name Function

A1 LED1 High-Side Current Source Output for Flash LED.

A2, B2 OUT Step-Up DC/DC Converter Output.

A3, B3 SW Drain Connection for Internal NMOS and Synchronous PMOS Switches.

A4, B4 GND Ground

B1 LED2 High-Side Current Source Output for Flash LED.

C1 LEDI/NTC Configurable as a High-Side Current Source Output for Indicator LED or Threshold Detector for

LED Temperature Sensing.

C2 TX1/TORCH/

GPIO1

Configurable as a RF Power Amplifier Synchronization Control Input (TX1), a Hardware Torch

Enable (TORCH), or a programmable general-purpose logic Input/Output (GPIO1).

C3 STROBE Active High Hardware Flash Enable. Drive STROBE high to turn on Flash pulse.

C4 IN Input Voltage Connection. Connect IN to the input supply, and bypass to GND with a minimum

4.7µF ceramic capacitor.

D1 ENVM/TX2/

GPIO2/INT

Configurable as an Active High Voltage Mode Enable (ENVM), Dual Polarity Power Amplifier

Synchronization Input (TX2), or Programmable General Purpose Logic Input/Output (GPIO2).

D2 SDA Serial Data Input/Output.

D3 SCL Serial Clock Input.

D4 HWEN Active Low Hardware Reset.

Ordering Information

Order Number Package Package Marking Supplied As No-Lead

LM3554TME TMD16CCA SF 250 units, Tape-and-Reel YES (NOPB)

LM3554TMX TMD16CCA SF 3000 units, Tape-and-Reel YES (NOPB)

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LM3554

Absolute Maximum Ratings (Note 1, Note

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

VIN, VSW, VOUT -0.3V to 6V

VSCL, VSDA, VHWEN, VSTROBE, VTX1/

TORCH, VENVM/TX2, VLED1, VLED2, VLEDI/

NTC

-0.3V to to (VIN

+0.3V) w/ 6.0V

max

Continuous Power Dissipation(Note 3) Internally Limited

Junction Temperature (TJ-MAX)+150°C

Storage Temperature Range -65°C to +150°C

Maximum Lead Temperature

(Soldering) (Note 4)

Operating Ratings (Note 1, Note 2)

VIN 2.5V to 5.5V

Junction Temperature (TJ) -30°C to +125°C

Ambient Temperature (TA)

(Note 5)

-30°C to +85°C

Thermal Properties

Junction-to-Ambient Thermal

Resistance (θJA), TMD16

Package(Note 6) 60°C/W

ESD Caution Notice National Semiconductor recommends that all integrated circuits be handled with appropriate

ESD precautions. Failure to observe proper ESD handling techniques can result in damage to the device.

Electrical Characteristics

Limits in standard typeface are for TA = +25°C. Limits in boldface type apply over the full operating ambient temperature range

(-30°C ≤ TA ≤ +85°C). Unless otherwise specified, VIN = 3.6V, VHWEN = VIN. (Note 2, Note 7)

Symbol Parameter Conditions Min Typ Max Units

Current Source Specifications

ILED

Current Source

Accuracy

600mA Flash

LED Setting,

VOUT = VIN

ILED1+ILED2 1128 1200 1284

ILED1 or ILED2 541 600 657

17mA Torch

Current

Setting, VHR =

500mV

ILED1+ILED2 30.4 33.8 37.2

VHR

Current Source

Regulation

Voltage (VOUT -

VLED)

600mA setting, VOUT = 3.75V 300 mV

IMATCH

LED Current

Matching 600mA setting, VLED = 3.2V 0.35 %

Step-Up DC/DC Converter Specifications

VREG

Output Voltage

Accuracy

2.7V ≤ VIN ≤ 4.2V, IOUT = 0mA,

VENVM = VIN, OV bit = 0 4.8 55.2 V

VOVP

Output Over-

Voltage

Protection Trip

Point(Note 8)

On Threshold, 2.7V ≤ VIN ≤ 5.5V 5.4 5.6 5.7

Off Threshold 5.3

RPMOS

PMOS Switch

On-Resistance IPMOS = 1A 150 mΩ

RNMOS

NMOS Switch

On-Resistance INMOS = 1A 150 mΩ

ICL

Switch Current

Limit(Note 9)

CL bits = 00 0.711 1.05 1.373

CL bits = 01 1.295 1.51 1.8

CL bits = 10 1.783 1.99 2.263

CL bits = 11 2.243 2.45 2.828

IOUT_SC

Output Short

Circuit Current

Limit

VOUT < 2.3V 550 mA

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LM3554

Symbol Parameter Conditions Min Typ Max Units

ILED/NTC Indicator Current LEDI/NTC bit

= 0

IND1, IND0 bits =

00 2.3

IND1, IND0 bits =

01 4.6

IND1, IND0 bits =

10 6.9

IND1, IND0 bits =

11 8.2

VTRIP

Comparator Trip

Threshold

LEDI/NTC bit = 1, 2.7V ≤ VIN ≤

5.5V 0.947 1.052 1.157 V

fSW

Switching

Frequency 2.7V ≤ VIN ≤ 5.5V 1.75 22.23 MHz

Quiescent

Supply Current Device Not Switching 630 µA

ISHDN

Shutdown

Supply Current 2.7V ≤ VIN ≤ 5.5V 3.5 6.6 µA

tTX

Flash-to-Torch

LED Current

Settling Time

TX_ Low to High, ILED1 + ILED2 =

1.2A to 180mA 20 µs

VIN_TH

VIN Monitor Trip

Threshold

VIN Falling, VIN Monitor Register =

0x01 (Enabled with VIN_TH = 3.1V) 2.95 3.09 3.23 V

TX1/TORCH/GPIO1, STROBE, HWEN, ENVM/TX2/GPIO2 Voltage Specifications

VIL Input Logic Low 2.7V ≤ VIN ≤ 5.5V 0 0.4 V

VIH Input Logic High 2.7V ≤ VIN ≤ 5.5V 1.2 VIN V

VOL

Output Logic

Low ILOAD = 3mA, 2.7V ≤ VIN ≤ 5.5V 400 mV

RTX1/TORCH

Internal Pull-

down Resistance

at TX1/TORCH

300 kΩ

RSTROBE

Internal Pull-

Down

Resistance at

STROBE

300 kΩ

I2C-Compatible Voltage Specifications (SCL, SDA)

VIL Input Logic Low 2.7V ≤ VIN ≤ 5.5V 0 0.4 V

VIH Input Logic High 2.7V ≤ VIN ≤ 5.5V 1.22 VIN V

VOL

Output Logic

Low (SCL) ILOAD = 3mA, 2.7V ≤ VIN ≤ 5.5V 400 mV

I2C-Compatible Timing Specifications (SCL, SDA) — See Figure 1

1/t1

SCL Clock

Frequency 400 kHz

Data In Setup

Time to SCL

High

100 ns

Data Out Stable

After SCL Low 0 ns

SDA Low Setup

Time to SCL Low

(Start)

160 ns

SDA High Hold

Time After SCL

High (Stop)

160 ns

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LM3554

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings are conditions under which operation of

the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see

the Electrical Characteristics table.

Note 2: All voltages are with respect to the potential at the GND pin.

Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ=150°C (typ.) and disengages at

TJ=135°C (typ.).

Note 4: For detailed soldering specifications and information, please refer to National Semiconductor Application Note 1112: Micro SMD Wafer Level chip Scale

Package (AN-1112)

Note 5: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be

derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = +125°C), the maximum power

dissipation of the device in the application (PD-MAX), and the junction-to-ambient thermal resistance of the part/package in the application (θJA), as given by the

following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX).

Note 6: Junction-to-ambient thermal resistance (θJA) is taken from a thermal modeling result, performed under the conditions and guidelines set forth in the

JEDEC standard JESD51-7. The test board is a 4-layer FR-4 board measuring 102mm x 76mm x 1.6mm with a 2x1 array of thermal via's. The ground plane on

the board is 50mm x 50mm. Thickness of copper layers are 36µm/18µm/18µm/36µm (1.5oz/1oz/1oz/1.5oz). Ambient temperature in simulation is 22°C, still air.

Power dissipation is 1W.

Note 7: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical (Typ) numbers are not guaranteed, but do represent the most likely

norm. Unless otherwise specified, conditions for typical specifications are: VIN = 3.6V and TA = +25°C.

Note 8: The typical curve for Over-Voltage Protection (OVP) is measured in closed loop using the typical application circuit . The OVP value is found by forcing

an open circuit in the LED1 and LED2 path and recording the peak value of VOUT. The value given in the Electrical Table is found in an open loop configuration

by ramping the voltage at OUT until the OVP comparator trips. The closed loop data can appear higher due to the stored energy in the inductor being dumped

into the output capacitor after the OVP comparator trips. At worst case is an open circuit condition where the output voltage can continue to rise after the OVP

comparator trips by approximately IIN×sqrt(L/COUT).

Note 9: The typical curve for Current Limit is measured in closed loop using the typical application circuit by increasing IOUT until the peak inductor current stops

increasing. The value given in the Electrical Table is measured open loop and is found by forcing current into SW until the current limit comparator threshold is

reached. Closed loop data appears higher due to the delay between the comparator trip point and the NFET turning off. This delay allows the closed loop inductor

current to ramp higher after the trip point by approximately 20ns × VIN/L

Note 10: Current Matching = Absolute Value((ILED1 - ILED2)/(ILED1 + ILED2)) × 100

Note 11: Current Accuracy = Absolute Value(ITARGET - (ILED1 + ILED2)) × 100

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FIGURE 1. I2C Timing

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LM3554