MAX1705/MAX1706
1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
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Pin Description
Boost DC-DC Converter Power Output. POUT is the source of the p-channel synchronous-rectifier MOSFET
switch. Connect an external Schottky diode from LX to POUT. The output current available from POUT is
reduced by the current drawn from the LDO linear-regulator output.
POUT16
On-Control Input. When ONA = high or ONB = low, the IC turns on. Connect ONA to OUT for normal
operation (Table 2).
ONA15
Off-Control Input. When ONB = high and ONA = low, the IC is off. Connect ONB to GND for normal
operation (Table 2).
ONB
14
Inductor Connection to the Drains of the p-Channel Synchronous Rectifier and n-Channel SwitchLX13
Power Ground for the Source of the n-channel power MOSFET switchPGND12
Low-Dropout Linear-Regulator Output. LDO sources up to 200mA. Bypass to GND with a 22µF capacitor.LDO9
Low-Battery Comparator Output. This open-drain, n-channel output is low when LBP < LBN.
Input hysteresis is 16mV.
LBO10
Switching-Mode Selection and External-Clock Synchronization Input:
• CLK/SEL = low: low-power, low-quiescent-current PFM mode.
• CLK/SEL = high: low-noise, high-power PWM mode. Switches at a constant frequency (300kHz). Full
output power is available.
• CLK/SEL = driven with an external clock: low-noise, high-power synchronized PWM mode.
Synchronizes to an external clock (from 200kHz to 400kHz).
Turning on the DC-DC converter with CLK/SEL = GND also serves as a soft-start function,
since peak inductor current is reduced.
CLK/SEL11
GroundGND5
Step-Up Converter Feedback Input, Used During Track Mode. IC power and low-dropout linear-regulator
input. Bypass OUT to GND with a 0.1µF ceramic capacitor placed as close to the IC as possible.
OUT6
Step-Up DC-DC Converter Feedback Input. Connect FB to a resistor voltage-divider between POUT and
GND to set the output voltage between 2.5V and 5.5V. FB regulates to 1.233V.
FB7
Low-Dropout Linear-Regulator Feedback Input. Connect FBLDO to a resistor voltage-divider between LDO
to GND to set the output voltage from 1.25V to V
OUT
- 0.3V (5.0V max). FBLDO regulates to 1.250V.
FBLDO8
Track-Mode Control Input for DC-DC Converter. In track mode, the boost-converter output is sensed at
OUT and set 0.3V above LDO to improve efficiency. Set TRACK to OUT for track mode. Connect TRACK to
GND for normal operation.
TRACK4
1.250V Reference Output. Bypass REF with a 0.33µF capacitor to GND. REF can source up to 50µA.REF3
PIN
Low-Battery Comparator Inverting Input. Common-mode range is 0.5V to 1.5V.LBN2
Low-Battery Comparator Noninverting Input. Common-mode range is 0.5V to 1.5V.LBP1
FUNCTIONNAME
