General Description
The MAX1760/MAX1760H are high-efficiency, low-noise,
step-up DC-DC converters intended for use in battery-
powered wireless applications. They combine low quies-
cent supply current (100µA) with a high 1MHz operating
frequency. Small external components and tiny 10-pin
TDFN and µMAX®packages make this device an excel-
lent choice for small hand-held applications. The
MAX1760 is activated by a logic-low ON signal while the
MAX1760H is activated by a logic-high ON input.
Both devices use a synchronous-rectified pulse-width-
modulation (PWM) boost topology to generate 2.5V to
5.5V outputs from a wide range of inputs, such as 1 to 3
alkaline or NiCd/NiMH cells or a single lithium-ion (Li+)
cell. Proprietary Idle-Mode™ circuitry significantly
improves light-load efficiency and smoothly transitions to
fixed-frequency PWM operation at higher load currents.
Low-noise, forced-PWM mode is available for applica-
tions requiring constant-frequency operation at all load
currents. PWM operation can also be synchronized to
an external clock to protect sensitive frequency bands
in communications equipment. Analog soft-start and
adjustable current limit permit optimization of efficiency,
external component size, and output voltage ripple.
Applications
Digital Cordless Phones PCS Phones
Wireless Handsets Handheld Instruments
Palmtop Computers Personal Communicators
Two-Way Pagers
Features
♦Up to 94% Efficiency
♦0.7V to 5.5V Input Range
♦Up to 800mA Output
♦Fixed 3.3V Output (or Adjustable from 2.5V to 5.5V)
♦PWM Synchronous-Rectified Topology
♦Low-Noise, Constant-Frequency Operation (1MHz)
♦0.1µA Logic-Controlled Shutdown
♦Synchronizable Switching Frequency
♦Adjustable Current Limit
♦Adjustable Soft-Start
♦10-Pin µMAX Package
♦10-Pin 3mm x 3mm TDFN Package
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
________________________________________________________________ Maxim Integrated Products 1
1
2
3
4
5
10
9
8
7
6
POUT
LX
PGNDFB
GND
REF
ISET
µMAX
TOP VIEW
CLK/SELOUT
ON (ON)
(ON) FOR MAX1760H
8
9
10
LX
POUT
ON (ON)
3
2
1
GND
REF
ISET
7PGND
4FB
6CLK/SEL
5OUT
TDFN
(3mm x 3mm)
MAX1760
MAX1760H
MAX1760
MAX1760H
PGND
FB GND
POUT
LX
ISET
OUT
REF
CLK/SEL
INPUT = 0.7V
TO VOUT
VOUT = 3.3V,
800mA
ON
MAX1760
Typical Operating Circuit
19-1660; Rev 3; 1/07
EVALUATION KIT
AVAILABLE
µMAX is a registered trademark of Maxim Integrated Products, Inc.
Idle Mode is a trademark of Maxim Integrated Products, Inc.
Pin Configurations
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
PART PIN-
PACKAGE
ON
LOGIC
PKG CODE
MAX1760ETB
10 TDFN-EP*
Low T1033-1
MAX1760EUB 10 µMAX Low U10-2
MAX1760HETB
10 TDFN-EP*
High T1033-1
MAX1760HEUB
10 µMAX High U10-2
*EP = Exposed paddle.
Note: All devices are specified over the -40°C to +85°C operating
temperature range.
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
2_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(CLK/SEL = FB = PGND = GND, ISET = REF, OUT = POUT, VOUT = 3.6V, TA= 0°C to +85°C. Typical values are at TA= +25°C,
unless otherwise noted.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation 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.
ON, ON, OUT, CLK/SEL to GND ..................................-0.3V to +6V
PGND to GND ..........................................................................±0.3V
LX to PGND .................................................-0.3V to (VPOUT + 0.3V)
POUT to OUT ...........................................................................±0.3V
REF, FB, ISET, POUT to GND.......................-0.3V to (VOUT + 0.3V)
Continuous Power Dissipation (TA= +70°C)
Single-Layer Board:
10-Pin µMAX
(derate 5.6mW/°C above +70°C).................................….444mW
10-Pin TDFN-EP (derate 18.5mW/°C above +70°C) .....1482mW
Multilayer Board:
10-Pin µMAX (derate 8.8mW/°C above +70°C) ..........….707mW
10-Pin TDFN-EP (derate 24.4mW/°C above +70°C) .....1951mW
Operating Temperature Range................................-40°C to +85°C
Junction Temperature ...........................................................+150°C
Storage Temperature Range .................................-65°C to +150°C
Lead Temperature (soldering, 10s)......................................+300°C
PARAMETER CONDITIONS
MIN TYP MAX
UNITS
DC-DC CONVERTER
Input Voltage Range (Note 1) 0.7 5.5 V
Minimum Startup Voltage ILOAD < 1mA, TA = +25°C (Note 2) 0.9 1.1 V
Temperature Coefficient of Startup Voltage ILOAD < 1mA
-2.3
mV/°C
Frequency in Startup Mode VOUT = 1.5V
125 500 1000
kHz
Internal Oscillator Frequency CLK/SEL = OUT 0.8 1 1.2
MHz
Oscillator Maximum Duty Cycle (Note 3) 80 86 90 %
External Clock Frequency Range 0.5 1.2
MHz
Output Voltage VFB < 0.1V, CLK/SEL = OUT, includes load
regulation for 0 < ILX < 0.55A
3.17
3.3
3.38
V
FB Regulation Voltage Adjustable output, CLK/SEL = OUT, includes
load regulation for 0 < ILX < 0.55A
1.215 1.240 1.270
V
FB Input Leakage Current VFB = 1.35V (TA = +25°C, MAX1760ETB,
MAX1760HETB)
0.01 100
nA
Load Regulation CLK/SEL = OUT, no load to full load
(0 < ILX < 1.0A)
-1.5
%
Output Voltage Adjust Range 2.5 5.5 V
Output Voltage Lockout Threshold Rising edge (Note 4)
2.00 2.15 2.30
V
ISET Input Leakage Current VISET = 1.25V (TA = +25°C, MAX1760ETB,
MAX1760HETB)
±0.01 ±50
nA
Supply Current in Shutdown V
ON = 3.6V, VON = 0V 0.1 5 µA
No-Load Supply Current CLK/SEL = GND (Note 5)
100 185
µA
No-Load Supply Current Forced-PWM Mode
CLK/SEL = OUT 2.5
mA
DC-DC SWITCHES
POUT Leakage Current VLX = 0, VOUT = 5.5V (TA = +25°C,
MAX1760ETB, MAX1760HETB) 0.1 10 µA
LX Leakage Current VLX = VOUT = 5.5V, in shutdown (TA =
+25°C, MAX1760ETB, MAX1760HETB) 0.1 10 µA
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS
(CLK/SEL = FB = PGND = GND, ISET = REF, OUT = POUT, VOUT = 3.6V, TA= -40°C to +85°C,unless otherwise noted.) (Note 7)
ELECTRICAL CHARACTERISTICS (continued)
(CLK/SEL = FB = PGND = GND, ISET = REF, OUT = POUT, VOUT = 3.6V, TA= 0°C to +85°C. Typical values are at TA= +25°C,
unless otherwise noted.)
PARAMETER CONDITIONS
MIN TYP MAX
N-channel
0.15 0.28
Switch On-Resistance P-channel
0.25 0.45
Ω
N-Channel Current Limit 1.0
1.25
1.6 A
P-Channel Turn-Off Current CLK/SEL = GND 20 60
120
mA
REFERENCES
Reference Output Voltage IREF = 0
1.230 1.250 1.270
V
Reference Load Regulation -1µA < IREF < +50µA 5 15 mV
Reference Supply Rejection 2.5V < VOUT < 5V 0.2 5 mV
LOGIC INPUTS
CLK/SEL Input Low Level 2.5V ≤ VOUT ≤ 5.5V 0.2 x
VOUT
V
CLK/SEL Input High Level 2.5V ≤ VOUT ≤ 5.5V 0.8 x
VOUT
V
1.1V ≤ VOUT ≤ 1.8V 0.2
ON, ON Input Low Level (Note 6) 1.8V ≤ VOUT ≤ 5.5V 0.4 V
1.1V ≤ VOUT ≤ 1.8V VOUT
- 0.2
ON, ON Input High Level (Note 6)
1.8V ≤ VOUT ≤ 5.5V 1.6
V
Input Leakage Current CLK/SEL, ON, ON (TA = +25°C,
MAX1760ETB, MAX1760HETB)
0.01
1µA
Minimum CLK/SEL Pulse Width
200
ns
Maximum CLK/SEL Rise/Fall Time
100
ns
PARAMETER CONDITIONS MIN MAX UNITS
DC-DC CONVERTER
Output Voltage VFB < 0.1V, CLK/SEL = OUT, includes load
regulation for 0 < ILX < 0.55A 3.17 3.38 V
FB Regulation Voltage Adjustable output, CLK/SEL = OUT, includes
load regulation for 0 < ILX < 0.55A 1.215 1.270 V
Internal Oscillator Frequency CLK/SEL = OUT 0.75 1.2 MHz
Oscillator Maximum Duty Cycle (Note 3) 80 90 %
Output Voltage Lockout Threshold Rising edge (Note 4) 2.00 2.30 V
Supply Current in Shutdown V
ON = 3.6V 5 µA
No-Load Supply Current CLK/SEL = GND (Note 5) 185 µA
DC-DC SWITCHES
N-channel 0.28
Switch On-Resistance P-channel 0.45 Ω
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
4_______________________________________________________________________________________
Note 1: Operating voltage—since the regulator is bootstrapped to the output, once started, the MAX1760 operates down
to 0.7V input.
Note 2: Startup is tested with the circuit shown in Figure 6.
Note 3: Defines maximum step-up ratio.
Note 4: The regulator is in startup mode until this voltage is reached. Do not apply full load current until the output exceeds 2.3V.
Note 5: Supply current into the OUT pin. This current correlates directly to the actual battery-supply current, but is reduced in
value according to the step-up ratio and efficiency.
Note 6: ON (MAX1760) and ON (MAX1760H) have a hysteresis of approximately 0.15 ×VOUT.
Note 7: Specifications to -40°C are guaranteed by design and not production tested.
100
0
0.0001 0.001 0.01 0.1 1
EFFICIENCY vs. OUTPUT CURRENT
VOUT = 3.3V
20
MAX1760 toc01
OUTPUT CURRENT (A)
EFFICIENCY (%)
40
70
90
60
80
10
30
50
A
B
C
A: VIN = 2.4V
B: VIN = 1.2V
C: VIN = 0.9V
= AUTO MODE
= FPWM MODE
MAX1760-02
100
0
0.0001 0.001 0.01 0.1 1
EFFICIENCY vs. OUTPUT CURRENT
VOUT = 5V
20
OUTPUT CURRENT (A)
EFFICIENCY (%)
40
70
90
60
80
10
30
50
A: VIN = 3.6V
B: VIN = 2.4V
C: VIN = 1.2V
= AUTO MODE
= FPWM MODE
A
B
C
MAXIMUM OUTPUT CURRENT
vs. INPUT VOLTAGE
MAX1760-03
0.1
1.00.5 1.5 2.0 2.5 3.0 3.5 4.0
0.3
0.2
0.5
0.4
0.8
0.7
0.6
0.9
INPUT VOLTAGE (V)
OUTPUT CURRENT (A)
VOUT = 3.3V
VOUT = 5V
ELECTRICAL CHARACTERISTICS (continued)
(CLK/SEL = FB = PGND = GND, ISET = REF, OUT = POUT, VOUT = 3.6V, TA= -40°C to +85°C,unless otherwise noted.) (Note 7)
Typical Operating Characteristics
(Circuit of Figure 2, VIN = 2.4V, VOUT = 3.3V, TA= +25°C, unless otherwise noted.)
PARAMETER CONDITIONS
MIN
MAX
UNITS
N-Channel Current Limit 1.0 1.6 A
REFERENCE
Reference Output Voltage IREF = 0
1.230 1.270
V
LOGIC INPUTS
CLK/SEL Input Low Level 2.5V ≤ VOUT ≤ 5.5V 0.2 x
VOUT
V
CLK/SEL Input High Level 2.5V ≤ VOUT ≤ 5.5V 0.8 x
VOUT
V
1.1V ≤ VOUT ≤ 1.8V 0.2
ON, ON Input Low Level (Note 6) 1.8V ≤ VOUT ≤ 5.5V 0.4 V
1.1V ≤ VOUT ≤ 1.8V VOUT + 0.2
ON, ON Input High Level (Note 6) 1.8V ≤ VOUT ≤ 5.5V 1.6 V
Input Leakage Current CLK/SEL, ON, ON 1 µA
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
_______________________________________________________________________________________ 5
NO-LOAD BATTERY CURRENT
vs. INPUT VOLTAGE
MAX1760-04
0.0
0.5
1.5
1.0
2.0
2.5
021345
INPUT VOLTAGE (V)
INPUT CURRENT (mA)
VOUT = 3.3V
VOUT = 5V
TOTAL SHUTDOWN CURRENT
(ILX + IOUT) vs. INPUT VOLTAGE
MAX1760-05
0.1
02146
1
10
INPUT VOLTAGE (V)
SHUTDOWN CURRENT (nA)
35
INTERNAL OSCILLATOR
FREQUENCY vs. TEMPERATURE
MAX1760-06
0.75
0.85
0.80
1.00
0.95
0.90
1.15
1.10
1.05
1.20
-40 10-15 35 6085
TEMPERATURE (°C)
FREQUENCY (MHz)
STARTUP VOLTAGE
vs. OUTPUT CURRENT
MAX1760-07
0.001 0.01 0.1 1
OUTPUT CURRENT (A)
STARTUP VOLTAGE (V)
3.0
0.0
0.5
1.0
1.5
2.0
2.5
CIRCUIT OF FIGURE 6
C
AB
B = +25°C
C = -40°C
A = +85°C
PEAK INDUCTOR CURRENT vs. VISET
MAX1760-08
0.0
0.4
0.2
0.8
0.6
1.2
1.0
1.4
0.1 0.5 0.70.3 0.9 1.1 1.3
VISET (V)
PEAK INDUCTOR CURRENT (A)
HEAVY-LOAD SWITCHING WAVEFORMS
MAX1760-09
C
0V
A
B
A = LX PIN, 5V/div
B = INDUCTOR CURRENT, 200mA/div
C = OUTPUT RIPPLE, 50mV/div AC-COUPLED
t = 400ns/div
LIGHT-LOAD SWITCHING WAVEFORMS
MAX1760-10
C
t = 400ns/div
A
B
A = LX PIN, 5V/div
B = INDUCTOR CURRENT, 200mA/div
C = OUTPUT RIPPLE, 50mV/div, AC-COUPLED
LOAD-TRANSIENT RESPONSE
MAX1760-11
t = 200ms/div
A
B
VIN = 1.1V, VOUT = 3.3V, IOUT = 0 AND 0.2A
A = IOUT, 100mA/div
B = VOUT, 50mV/div, AC-COUPLED
LINE-TRANSIENT RESPONSE
MAX1760-12
400µs/div
A
B
VIN = 2.4V TO 1.4V, IOUT = 70mA
A = VIN, 1V/div
B = VOUT, 5mA/div, AC-COUPLED
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = 2.4V, VOUT = 3.3V, TA= +25°C, unless otherwise noted.)
10
ON MAX1760H Enable Input. When ON is high, the IC is on. Connect to OUT for normal operation.
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
6_______________________________________________________________________________________
NOISE SPECTRUM
MAX1760-13
1010.1
16
4
0
12
8
FREQUENCY (MHz)
NOISE (mVRMS)
TURN-ON WAVEFORMS
NO SOFT-START COMPONENTS
MAX1760-14
OV
C
A
B
t = 2ms/div
A = ON, 5V/div
B = INPUT CURRENT, 500mA/div
C = VOUT, 2V/div
SOFT-START WAVEFORMS
RSS = 500kΩ, CSS = 0.1µF
MAX1760-15
0V
C
A
B
2.00ms/div
A = ON, 5V/div
B = INPUT CURRENT, 100mA/div
C = VOUT, 2V/div
Pin Description
Typical Operating Characteristics (continued)
(Circuit of Figure 2, VIN = 2.4V, VOUT = 3.3V, TA= +25°C, unless otherwise noted.)
NAME FUNCTION
1ISET
N-Channel Current-Limit Control. For maximum current limit, connect to REF. To reduce current, supply a
voltage between REF and GND by means of a resistive voltage-divider. If soft-start is desired, connect a
capacitor from ISET to GND. When ON = high, or VREF <80% of nominal value, an on-chip 100kΩswitched
resistor discharges this pin to GND.
2REF 1.250V Voltage Reference Bypass. Connect a 0.22µF ceramic bypass capacitor to GND. Up to 50µA of
external load current is allowed.
PIN
3GND Ground. Connect to PGND with short trace.
4FB DC-DC Converter Feedback Input. To set fixed output voltage of +3.3V, connect FB to ground. For
adjustable output of 2.5V to 5.5V, connect to a resistive divider from OUT to GND. FB set point = 1.24V.
8LX Inductor Connection
7PGND Source of N-Channel Power MOSFET Switch
6CLK/SEL
Clock Input for the DC-DC Converter. Also serves to program operating mode of switcher as follows:
CLK/SEL = LO: Normal operation—operates at a fixed frequency, automatically switching to low-power
mode if load is minimized.
CLK/SEL = HI: Forced-PWM mode—operates in low-noise, constant-frequency mode at all loads.
CLK/SEL = Clocked: Forced-PWM mode with the internal oscillator synchronized to CLK in 500kHz to
1200kHz range.
5OUT IC Power, Supplied from the Output. Bypass to GND with a 0.68µF ceramic capacitor, and connect to POUT
with a series 4.7Ωresistor (Figure 2).
9 POUT Power Output. P-channel synchronous-rectifier source.
—EP Exposed Paddle (TDFN Package Only). Internally connected to GND. Connect to a large ground plane to
maximize thermal dissipation. Do not use as sole ground connection.
ON MAX1760 Enable Input. When ON is low, the IC is on. Connect to GND for normal operation.
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
_______________________________________________________________________________________ 7
Detailed Description
The MAX1760 is a highly efficient, low-noise power sup-
ply for portable RF and hand-held instruments. It com-
bines a boost switching regulator, N-channel power
MOSFET, P-channel synchronous rectifier, precision
reference, and shutdown control (Figure 1).
The DC-DC converter boosts a 1-cell to 3-cell battery
voltage input to a fixed 3.3V or adjustable voltage
between 2.5V and 5.5V. An external Schottky diode is
required for output voltages greater than 4V. The
MAX1760 guarantees startup with an input voltage as
low as 1.1V and remains operational down to an input
of just 0.7V. It is optimized for use in cellular phones
and other applications requiring low noise and low qui-
escent current for maximum battery life. It features
fixed-frequency operation at medium and heavy loads,
but at light loads, switches only as needed for optimum
efficiency. This device is also capable of constant-fre-
quency (1MHz), low-noise PWM operation at all load
currents, or frequency-synchronized PWM operation
when connected to an external clock. Table 1 lists
some typical outputs. Shutdown reduces quiescent cur-
rent to just 1µA. Figure 2 shows the standard applica-
tion circuit for the MAX1760.
Step-Up Converter
During DC-DC converter operation, the internal N-chan-
nel MOSFET switch turns on for the first part of each
cycle, allowing current to ramp up in the inductor and
store energy in a magnetic field. During the second
part of each cycle, the MOSFET turns off and inductor
current flows through the synchronous rectifier to the
2.15V
IC POWER
1.25V REFERENCE
UNDERVOLTAGE LOCKOUT
STARTUP
OSCILLATOR
OSCILLATOR
1MHz
CONTROLLER
MODE
PCH
NCH
EN D
EN
POUT
LX
PGND
OSCOSC
MODE
CLK/SEL
ISET
FB
EN
Q
REF
FB
ISET
GND
CLK/SEL
ON RDY
REF GND
ON
(MAX1760H)
OUT
MAX1760
ON
(MAX1760)
Figure 1. Functional Diagram
FB PGNDGND
POUT
LX
ISET
OUT
REF
CLK/SEL
VIN = 2.4V
VOUT = 3.3V,
800mA
ON
MAX1760
3.3µH
0.68µF
4.7Ω
33µF
0.22µF
100µF
Figure 2. Standard Application Circuit
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
8_______________________________________________________________________________________
output filter capacitor and the load. As the energy
stored in the inductor is depleted, the current ramps
down and the synchronous rectifier turns off. At light
loads, the device operates at fixed frequency or only as
needed to maintain regulation, depending on the
CLK/SEL setting (Table 2).
Normal Operation
Pulling CLK/SEL low selects the MAX1760’s normal
operating mode. In this mode, the device operates in
PWM when driving medium-to-heavy loads, and auto-
matically switches to PFM if the load requires less
power. PFM operation allows higher efficiency than
PWM under light-load conditions.
Forced-PWM Operation
When CLK/SEL is high, the MAX1760 operates in a low-
noise PWM-only mode. During forced-PWM operation,
the MAX1760 switches at a constant frequency (1MHz)
and modulates the MOSFET switch pulse width to con-
trol the power transferred per cycle to regulate the out-
put voltage. Switching harmonics generated by
fixed-frequency operation are consistent and easily fil-
tered. See the Noise Spectrum plot in the Typical
Operating Characteristics.
Synchronized-PWM Operation
The MAX1760 can be synchronized in PWM mode to an
external frequency of 500kHz to 1.2MHz by applying an
external clock signal to CLK/SEL. This allows interfer-
ence to be minimized in wireless applications. The syn-
chronous rectifier is active during synchronized-PWM
operation.
Synchronous Rectifier
The MAX1760 features an internal, P-channel synchro-
nous rectifier to enhance efficiency. Synchronous recti-
fication provides 5% improved efficiency over similar
nonsynchronous boost regulators. In PWM mode, the
synchronous rectifier is turned on during the second
half of each switching cycle. In low-power mode, an
internal comparator turns on the synchronous rectifier
when the voltage at LX exceeds the boost regulator
output, and turns it off when the inductor current drops
below 60mA. When setting output voltages greater than
4V, an external 0.5A Schottky diode must be connected
in parallel with the on-chip synchronous rectifier.
Low-Voltage Startup Oscillator
The MAX1760 uses a CMOS, low-voltage startup oscil-
lator for a 1.1V guaranteed minimum startup input volt-
age. At startup, the low-voltage oscillator switches the
N-channel MOSFET until the output voltage reaches
2.15V. Above this level, the normal boost-converter
feedback and control circuitry take over. Once the
device is in regulation, it can operate down to 0.7V
input since internal power for the IC is bootstrapped
from the output through OUT. Do not apply full load
until the output exceeds 2.3V.
Shutdown
The MAX1760 has a shutdown mode that reduces qui-
escent current to 0.1µA. During shutdown (ON = high
on MAX1760, ON = low on MAX1760H), the reference
and all feedback and control circuitry are off. During
shutdown, the output voltage is one diode drop below
the input voltage.
Table 1. Typical Available Output Current
5.03.63 750
3.32.4
2
3.31.21
OUTPUT VOLTAGE
(V)
INPUT VOLTAGE
(V)
NUMBER OF NiCd/NiMH
CELLS
800
350
OUTPUT CURRENT
(mA)
5.02.4 500
Table 2. Selecting the Operating Mode
CLK/SEL MODE FEATURES
0Normal operation High efficiency at all loads. Fixed frequency at all but light loads.
1Forced PWM Low noise, fixed frequency at all loads.
External clock
500kHz to 1.2MHz Synchronized PWM Low noise, fixed frequency at all loads.
Reference
The MAX1760 has an internal 1.250V ±1% reference.
Connect a 0.22µF ceramic bypass capacitor from REF
to GND within 0.2in (5mm) of the REF pin. REF can
source up to 50µA of external load current.
Design Procedure
Setting the Output Voltages
For a fixed 3.3V output, connect FB to GND. To set
other output voltages between 2.5V and 5.5V, connect
a resistor voltage-divider to FB from OUT to GND
(Figure 3). The input bias current into FB is <20nA,
allowing large-value divider resistors without sacrificing
accuracy. Connect the resistor voltage-divider as close
to the IC as possible, within 0.2in (5mm) of FB. Choose
R2 of 270kΩor less, then calculate R1 using:
where VFB, the boost-regulator feedback set point, is
1.24V.
Setting the Switch Current Limit
and Soft-Start
The ISET pin adjusts the inductor current limit and
implements soft-start. With ISET connected to REF, the
inductor current limits at 1.25A. With ISET connected to
a resistive divider set from REF to GND, the current limit
is reduced according to:
Implement soft-start by placing a resistor from ISET to
REF and a capacitor from ISET to GND. In shutdown,
ISET is discharged to GND through an on-chip 100kΩ
resistor. At power-up, ISET is 0V and the LX current is
zero. As the capacitor voltage rises, the current
increases and the output voltage rises. The soft-start
I 1.25A V
1.25V
LIM ISET
=
R1 R2
V
V1
OUT
FB
=−
MAX1760
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
_______________________________________________________________________________________ 9
Figure 3. Connecting Resistors for External Feedback
ISET
REF
MAX1760
RSS
CSS
0.22µF
tSS = RSSCSS
RSS ≥ 470kΩ
ILIM = 1.25A
Figure 4. Soft-Start with Maximum Switch Limit Current
ISET
REF
MAX1760
RSS1
CSS
0.22µF
RSS2
tSS = (RSS1 II RSS2) CSS
ILIM = 1.25A RSS1 + RSS2
RSS2
( )
RSS1 ≥ 470kΩ
Figure 5. Soft-Start with Reduced Switch Current Limit
FB
PGND GND
POUT
LX
ISET
OUT
REF
CLK/SEL
V
IN
= 2.4V
V
OUT
ON
MAX1760
100µF
3.3µH
0.68µF
4.7Ω
33µF
0.22µFR1
R2
-
1
R1 = R2
( )
VOUT
VFB
V
FB
= 1.24V
time constant is:
where RSS ≥470kΩ.
Placing a capacitor across the lower resistor of the cur-
rent-limiting resistive divider provides both current-limit
and soft-start features simultaneously (Figures 4 and 5).
Inductor Selection
The MAX1760’s high switching frequency allows the
use of a small 3.3µH surface-mount inductor. The cho-
sen inductor should generally have a saturation current
rating exceeding the N-channel switch current limit;
however, it is acceptable to bias the inductor current
into saturation by as much as 20% if a slight reduction
in efficiency is acceptable. Lower current-rated induc-
tors may be used if ISET is employed to reduce the
peak inductor current (see the Setting the Switch
Current Limit and Soft-Start section). For high efficien-
cy, choose an inductor with a high-frequency ferrite
core material to reduce core losses. To minimize radiat-
ed noise, use a toroid or shielded inductor. See Table 3
for suggested components and Table 4 for a list of
component suppliers. Connect the inductor from the
battery to the LX pin as close to the IC as possible.
External Diode
For output voltages greater than 4V, an external
Schottky diode must be connected from LX to POUT, in
parallel with the on-chip synchronous rectifier (Figure
6). The diode should be rated for 0.5A. Representative
devices are Motorola MBR0520L, Nihon EP05Q03L, or
generic 1N5817. This external diode is also recom-
mended for applications that must start with input volt-
ages at or below 1.8V. The Schottky diode carries
current during startup and after the synchronous rectifi-
er turns off; thus, its current rating only needs to be
500mA. Connect the diode as close to the IC as possi-
ble. Do not use ordinary rectifier diodes; their slow
switching speeds and long reverse-recovery times ren-
der them unacceptable. For circuits that do not require
startup with inputs below 1.8V and have an output of 4V
or less, no external diode is needed.
Input and Output Filter Capacitors
Choose input and output filter capacitors that will ser-
vice the input and output peak currents with accept-
able voltage ripple. Choose input capacitors with
working voltage ratings over the maximum input volt-
tRC
SS SS SS
=
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
10 ______________________________________________________________________________________
Table 3. Component Selection Guide
Sanyo POSCAP series
Sumida CDRH5D18
Kemet T510 series
TOKO type D518LC
—
Sumida CDRH4D28
Surface mount
AVX TPS seriesTOKO type D52LC
CAPACITORSINDUCTORSPRODUCTION METHOD
—
Motorola MBR0520L
—
EIC SB series
DIODES
Table 4. Component Suppliers
Note: Please indicate that you are using the MAX1760 when
contacting these component suppliers.
FB
PGND GND
POUT
MRB0520L
LX
ISET
OUT
REF
CLK/SEL
VIN = 0.7V
TO VOUT
VOUT
ON
MAX1760 100µF
3.3µH
0.68µF
4.7Ω
33µF
0.22µF
Figure 6. Connection with External Schottky Diode for Output
Voltages Greater than 4V, or to Assist Low-Voltage Startup
SUPPLIER PHONE
AVX USA: 843-448-9411
EIC USA: 916-941-0712
Kemet USA: 810-287-2536
Motorola USA: 408-629-4789
Japan: 81-45-474-7030
Sumida USA: 847-956-0666
Japan: 011-81-3-3667-3302
TOKO USA: 847-297-0070
age, and output capacitors with working voltage ratings
higher than the output.
The input filter capacitor reduces peak currents drawn
from the input source and also reduces input switching
noise. The input voltage source impedance determines
the required value of the input capacitor. When operat-
ing directly from one or two NiMH cells placed close to
the MAX1760, use a single 33µF low-ESR input filter
capacitor. With higher impedance batteries, such as
alkaline and Li+, a higher value input capacitor may
improve efficiency.
The output filter capacitor reduces output ripple voltage
and provides the load with transient peak currents
when necessary. For the output, a 100µF, low-equiva-
lent-series-resistance (ESR) capacitor is recommended
for most applications.
Sanyo POSCAP, Panasonic SP/CB, and Kemet T510
are good low-ESR capacitors. Low-ESR tantalum
capacitors offer a good tradeoff between price and
performance. Do not exceed the ripple current ratings
of tantalum capacitors. Avoid aluminum electrolytic
capacitors; their high ESR typically results in higher
output ripple voltage.
Other External Components
Two ceramic bypass capacitors are required for proper
operation. Bypass REF to GND with 0.22µF. Also,
bypass OUT to GND with a 0.68µF ceramic capacitor,
and connect OUT to POUT with a 4.7Ωresistor. Each of
these components should be placed as close to its
respective IC pins as possible, within 0.2in (5mm).
Table 4 lists suggested suppliers.
Layout Considerations
High switching frequencies and large peak currents
make PCB layout a critical part of design. Poor design
causes excessive EMI and ground bounce, both of
which can cause instability or regulation errors by cor-
rupting the voltage and current feedback signals.
Power components—such as the inductor, converter IC,
filter capacitors, and output diode—should be placed
as close together as possible, and their traces should
be kept short, direct, and wide. Keep the voltage feed-
back network very close to the IC, within 0.2in (5mm) of
the FB pin. Keep noisy traces, such as those from the
LX pin, away from the voltage feedback network and
guarded from them using grounded copper. Refer to the
MAX1760 evaluation kit for a full PCB example.
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
______________________________________________________________________________________ 11
TRANSISTOR COUNT: 1361
Chip Information
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
10LUMAX.EPS
PACKAGE OUTLINE, 10L uMAX/uSOP
1
1
21-0061
REV.DOCUMENT CONTROL NO.APPROVAL
PROPRIETARY INFORMATION
TITLE:
TOP VIEW
FRONT VIEW
1
0.498 REF
0.0196 REF
S
6°
SIDE VIEW
α
BOTTOM VIEW
0° 0° 6°
0.037 REF
0.0078
MAX
0.006
0.043
0.118
0.120
0.199
0.0275
0.118
0.0106
0.120
0.0197 BSC
INCHES
1
10
L1
0.0035
0.007
e
c
b
0.187
0.0157
0.114
H
L
E2
DIM
0.116
0.114
0.116
0.002
D2
E1
A1
D1
MIN
-A
0.940 REF
0.500 BSC
0.090
0.177
4.75
2.89
0.40
0.200
0.270
5.05
0.70
3.00
MILLIMETERS
0.05
2.89
2.95
2.95
-
MIN
3.00
3.05
0.15
3.05
MAX
1.10
10
0.6±0.1
0.6±0.1
Ø0.50±0.1
H
4X S
e
D2
D1
b
A2 A
E2
E1 L
L1
c
α
GAGE PLANE
A2 0.030 0.037 0.75 0.95
A1
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
12 ______________________________________________________________________________________
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
______________________________________________________________________________________ 13
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
6, 8, &10L, DFN THIN.EPS
H
1
2
21-0137
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
______________________________________________________________________________________ 13
MAX1760/MAX1760H
0.8A, Low-Noise, 1MHz,
Step-Up DC-DC Converter
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
14 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
©2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
Revision History
Pages changed at Rev 3: 1, 2, 6, 11, 14
COMMON DIMENSIONS
SYMBOL MIN. MAX.
A0.700.80
D2.903.10
E2.903.10
A1 0.00 0.05
L0.200.40
PKG. CODE N D2 E2 eJEDEC SPEC b[(N/2)-1] x e
PACKAGE VARIATIONS
0.25 MIN.k
A2 0.20 REF.
2.30±0.101.50±0.106T633-1 0.95 BSC MO229 / WEEA 1.90 REF0.40±0.05
1.95 REF0.30±0.050.65 BSC2.30±0.108T833-1
2.00 REF0.25±0.050.50 BSC2.30±0.1010T1033-1
2.40 REF0.20±0.05- - - - 0.40 BSC1.70±0.10 2.30±0.1014T1433-1
1.50±0.10
1.50±0.10
MO229 / WEEC
MO229 / WEED-3
0.40 BSC - - - - 0.20±0.05 2.40 REFT1433-2 14 2.30±0.101.70±0.10
T633-2 6 1.50±0.10 2.30±0.10 0.95 BSC MO229 / WEEA 0.40±0.05 1.90 REF
T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF
T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF
-DRAWING NOT TO SCALE-
H2
2
21-0137
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
2.30±0.10 MO229 / WEED-3 2.00 REF0.25±0.05
0.50 BSC
1.50±0.1010T1033-2