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FAN4855

500mA High Efficiency Boost Regulator with Adjustable Output, Shutdown and Low Battery Detect

Fairchild Semiconductor 

December 2005

FAN4855

500mA High Efficiency Boost Regulator with Adjustable

Output, Shutdown and Low Battery Detect

Features

■ Low power PFM boost regulator

■ Input voltage range is from 1.6V to 4.5V

■ Output voltage range is from 3V to 5V

■ 500mA maximum load current capability

■ 95% efficient power conversion

■ 2-3 cell and single cell Li-Ion systems

■ Variable on-time Pulse Frequency Modulation (PFM)

■ Internal synchronous rectifier (no need for external

diode)

■ Low-battery detection

■ Logic controlled shutdown with true-load disconnect

■ Low (80µA) quiescent current

■ TSSOP-8 Package

Applications

■ DSCs

■ PDAs

■ Cell phones, smart phones

■ Portable instrumentations

■ 2-3 AA / AAA cells operated devices

■ Single cell Li-Ion operated devices

General Description

The FAN4855 is a low power boost regulator designed

for low voltage DC to DC conversion in 2-cell battery

powered systems such as digital cameras, cell phones

and PDAs. The converter starts-up at 1.3V and operates

after the start at an input voltage as low as 1V. Output

voltage can be adjusted by external resistors from 3.3V

to 5V with a maximum load current of 0.5A. Quiescent

current in shut-down mode is less than 10µA, which

maximizes the battery live time. The ON time changes

with the input voltage to maintain the ripple current con-

stant and to provide the highest efficiency over a wide

load range—while maintaining low peak currents in the

boost inductor. The combination of built-in power transis-

tors, synchronous rectification and low supply current,

make the FAN4855 ideal for portable applications. The

FAN4855 is available in 8-lead TSSOP package.

Ordering Information (TA = -40°C to +85°C)

Part Number

FAN4855MTC

FAN4855MTCX

Package

8 Pin TSSOP

8 Pin TSSOP

Packing

Rails

Tape and Reel

Typical Application

Input 1.6V

to 4.5V

On

Off

Low Battery

Detect In

Low Battery

Detect Out

FAN4855

1 VIN

GND 8

2 SHDN VL 7

3 LBI

4 LB0

VOUT 6

FB 5

Output 3.3V to 5V

up to 0.5A

©2005 Fairchild Semiconductor Corporation

1

FAN4855 Rev. 1.0.1

www.fairchildsemi.com

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