IRU3138

1

Rev. 1.0

01/29/04

www.irf.com

DESCRIPTION

The IRU3138 controller IC is designed to provide a low

cost synchronous Buck regulator for voltage tracking

applications such DDR memory and general purpose

on-board DC to DC converter. Modern micro processors

combined with DDR memory, need high-speed bandwidth

data bus which requires a particular bus termination volt-

age. This voltage will be tightly regulated to track the

half of chipset voltage for best performance. The IRU3138

together with two N-channel MOSFETs, provide a low

cost solution for such applications. This device features

a programmable frequency set from 200KHz to 400KHz,

under-voltage lockout for both Vcc and Vc supplies, an

external programmable soft-start function as well as

output under-voltage detection that latches off the de-

vice when an output short is detected.

1A Peak Output Drive Capability

0.8V Precision Reference Voltage Available

Shuts off both drivers at shorted output

and shutdown

200KHz to 400KHz operation set by an external

resistor

Soft-Start Function

Uncommitted Error Amplifier available for DDR

voltage tracking application

Protects the output when control FET is shorted

Synchronous Controller in 14-Pin Package

PACKAGE ORDER INFORMATION

FEATURES

SYNCHRONOUS PWM CONTROLLER

FOR TERMINATION POWER SUPPLY APPLICATIONS

DEVICE

PACKAGE

0 To 70

IRU3138CS

14-Pin Plastic SOIC NB (S)

Data Sheet No. PD94701

APPLICATIONS

DDR memory source sink Vtt application

Graphic Card

Low cost on-board DC to DC such as

5V to 3.3V, 2.5V or 1.8V

TYPICAL APPLICATION

IRU3138

U1

Vcc

Vc

HDrv

LDrv

Fb

Gnd

Comp

SS/SD

C1

0.1uF

C2

1uF

C5

0.1uF

C7

3300pF

R3

13K

Q1

IRF7460

Q2

IRF7456

L2

3.3uH

L1

1uH

C3

2x 47uF

C4

47uF

Vtt

1.25V @ 10A

C6

2x 150uF

40m

V

12V

PGnd

Rt

R1

1K

R2

1K

DDR

Memory

(2.5V)

5V

D1

BAT54