PWM CONTROL 3A STEP-DOWN CONVERTER

2007-6-6

1/7

FSP3131

PIN ASSIGNMENT

(Top View)

PIN DESCRIPTION

Pin Number Pin Name

Pin Description

1

FB

Feedback Pin

2

EN

Enable Input Pin

H: Normal operation(Step-down operation)

L: Step-down operation stopped(All circuits deactivated)

3

OCSET

Add an external resistor to set max output current

4

VCC

IC power supply pin

5,6

OUTPUT

Switch pin. Connect external inductor/diode here. Minimize trace area at this pin to

reduce EMI.

7,8

VSS

GND pin

TYPICAL APPLICATION

Cellular Phones

PC Motherboard

LCD Monitor

Graphic Card

DVD-Video Player

Telecom Equipment

ADSL Modem

Printer and other Peripheral Equipment

Microprocessor core supply

Networking power supply

VCC

VSS

VSS

OUTPUT

OUTPUT

8

7

6

5

1

2

3

4

FB

EN

OCSET

GENERAL DESCRIPTION

FSP3131 consists of step-down switching regulator

with PWM control. These devices include a

reference voltage source, oscillation circuit, error

amplifier and internal PMOS.

FSP3131 provides low-ripple power, high efficiency,

and excellent transient characteristics. The PWM

control circuit is able to vary the duty ratio linearly

from 0 up to 100%. This converter also contains an

error amplifier circuit as well as a soft-start circuir

that prevents overshoot at startup. An enable

function, an over current protect function and a

short circuit protect function are built inside, and

when OCP or SCP happens, the operation

frequency will be reduced from 300KHz to 30KHz.

Also, an internal compensation block is built in to

minimum external component count.

With the addition of an internal P-channel Power

MOS, a coil, capacitors, and a diode connected

externally, these ICs can function as step-down

switching regulators. They serve as ideal power

supply units for portable devices when coupled with

the

SOP8L

mini-package,

providing

such

outstanding features as low current consumption.

Since this converter can accommodate an input

voltage up to 23V, it is also suitable for the operation

via an AC adapter.

FEATURES

Input voltage: 3.6V to 23V.

Output voltage: 0.8V to VCC.

Duty ratio: 0% to 100% PWM control

Oscillation frequency: 300KHz typ.

Soft-start, Current limit, Enable function

Thermal Shutdown function

Built-in internal SW P-channel MOSFET

SOP8L Package.