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FAN5308

800mA High-Efficiency Step-Down DC-DC Converter

Fairchild Semiconductor 

June 2007

FAN5308

tm

800mA High-Efficiency Step-Down DC-DC Converter

Features

■ 96% efficiency, synchronous operation

■ Adjustable output voltage options from 0.8V to VIN

■ 2.5V to 5.5V input voltage range

■ Up to 800mA output current

■ Fixed-frequency 1.3MHz PWM operation

■ High-efficiency, power-save mode

■ 100% duty cycle low-dropout operation

■ Soft-start

■ Output over-voltage protection

■ Dynamic output voltage positioning

■ 25µA quiescent current

■ Thermal shutdown and short-circuit protection

■ Pb-free 3x3mm 6-lead MLP package

Applications

■ Pocket PCs, PDAs

■ Cell phones

■ Battery-powered portable devices

■ Digital cameras

■ Hard disk drives

■ Set-top boxes

■ Point-of-load power

■ Notebook computers

■ Communications equipment

Description

Designed for use in battery-powered applications, the

FAN5308 is a high-efficiency, low-noise synchronous

PWM current mode and pulse skip (power-save) mode

DC-DC converter. It can provide up to 800mA of output

current over an input range from 2.5V to 5.5V. The output

voltage can be externally adjusted over a range of 0.8V

to 5.5V by means of an external voltage divider.

At moderate and light loads, pulse skipping modulation is

used. Dynamic voltage positioning is applied and the

output voltage is shifted 0.8% above nominal value for

increased headroom during load transients. At higher

loads, the system automatically switches over to current

mode PWM control, operating at 1.3MHz. A current

mode control loop with fast transient response ensures

excellent line and load regulation. To achieve high effi-

ciency and ensure long battery life, the quiescent current

is reduced to 25µA in power-save mode, and the supply

current drops below 1µA in shut-down mode. The

FAN5308 is available in a 3x3mm 6-lead MLP package.

Ordering Information

Product Number

FAN5308

Output Voltage

Adjustable

Package Type

3x3mm 6-Lead MLP

Order Code

FAN5308MPX

Typical Application

CIN

10μF

VIN

1

PGND

2

EN

3

P1

(AGND)

SW

6

3.3μH

5 NC

R1

FB

4

5KΩ

R2 10KΩ

VOUT

1.2V (800mA)

COUT

2 x 10μF

© 2005 Fairchild Semiconductor Corporation

FAN5308 Rev. 1.0.2

Figure 1. Typical Application

www.fairchildsemi.com

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