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MAX1703

1-Cell to 3-Cell, High-Power (1.5A),

Low-Noise, Step-Up DC-DC Converter

8 _______________________________________________________________________________________

_______________Detailed Description

The MAX1703 is a highly efficient, low-noise power

supply for portable RF and data-acquisition instru-

ments. It combines a boost switching regulator, N-

channel power MOSFET, P-channel synchronous

rectifier, precision reference, shutdown control, versa-

tile gain block, and power-good (POK) comparator

(Figure 1) in a 16-pin narrow SO package.

The switching DC-DC converter boosts a 1- to 3-cell

input to a fixed 5V or an adjustable output between

2.5V and 5.5V. Typically the MAX1703 starts from a

low, 0.9V input and remains operational down to 0.7V.

The MAX1703 is optimized for use in cellular phones

and other applications requiring low noise during full-

power operation, as well as low quiescent current for

maximum battery life in low-power mode and shut-

down. It features constant-frequency (300kHz), low-

noise PWM operation with up to 1.5A output capability.

See Table 1 for typical outputs. A low-quiescent-cur-

rent, low-power mode offers an output up to 150mA

and reduces quiescent power consumption to 300µW.

In shutdown mode, the quiescent current is further

reduced to just 1µA. Figure 2 shows the standard appli-

cation circuit for the MAX1703.

2.15V

IC POWER

1.25V

DUAL

MODE/

OUT

REFERENCE

UNDERVOLTAGE LOCKOUT

START-UP

OSCILLATOR

300kHz

OSCILLATOR

PFM/PWM

CONTROLLER

PFM/PWM

POUT

LXN

LXP

PGND

COMPARATOR

OSC

MODE

OUT

REF

POKIN

GND

CLK/SEL

RDY

REF

OUT

MAX1703

POK

GAIN

BLOCK

REF

AIN

Figure 1. Functional Block Diagram

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

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