DESCRIPTION

KEY FEA TURES

s 5-Bit Programmable Output For CPU Core

Supply

s Power Solution For Pentium II Processors

s No Sense Resistor Required For Short-Circuit

Current Limiting

s Soft-Start And Hiccup-Mode Current

Limiting Functions

s Modulated Constant Off-Time Control

Mechanism For Fast Transient Response And

Simple System Design

s Power Good Flag

s Over-Voltage Pin Can Drive SCR Crowbar Or

Turn Off Signal Silver-Box Power Supply

The LX1669 is a Monolithic Switching

Regulator Controller IC designed to

provide a low cost, high performance

adjustable power supply for advanced

microprocessors and other applications

requiring a very fast transient response

and a high degree of accuracy. It provides

a programmable switching regulator out-

other processors.

Programmable Synchronous Recti-

fier Driver for CPU Core.

The main

output is adjustable from 1.3 to 3.5V using

a TTL-compatible 5-bit digital code to

meet Intel specifications. The IC can read

the signal from a DIP-switch, hardwired to

Pentium II processor’s pins or from soft-

ware. The 5-bit code adjusts the output

voltage between 1.30 and 2.05V in 50mV

increments, and between 2.0 and 3.5V in

100mV increments. The device can drive

dual MOSFET’s resulting in typical effi-

ciencies of 85 – 90%, even with loads in

excess of 10A.

Short-circuit Current Limiting with-

out Expensive Current Sense Resis-

tors. The current sensing mechanism can

use a PCB trace resistance or the parasitic

resistance of the main inductor.

For

applications requiring a high degree of

accuracy, a conventional sense resistor

can be used.

Ultra-Fast Transient Response Re-

duces System Cost. The fixed frequency

modulated off-time architecture results in

the fastest transient response for a given

inductor.

Small Package Size.

The LX1669 is

available in an economical 16-pin narrow

body SOIC package.

PRODUCT HIGHLIGHT

OF

APPLICA TIONS

s Socket 7 Processor Supplies

s Pentium II Processor Supplies

s Deschutes CPU & L2-Cache Memory

Supplies

s Voltage Regulator Modules

s General Purpose And Microprocessor

DC:DC Supplies

Note: All surface-mount packages are available in Tape & Reel, append the letter "T" to part number. (i.e. LX1669CDT)

P ACKAGE ORDER INFO

T

0 to 70

LX1669CD

Copyright © 1999

Rev. 1.0

4/99

1

5V

CPU Core

V

CORE

C2

1500µFx3

Q1

IRL3102

Q2

IRL3303

L1

2.5µH

C1

1500µF x 6

R

SENSE

2.5m

Ω

C8

1µF

TDRV

V

CC12

V

CC5

PWRGD

OVP

VID0

VID1

VID2

PGND

BDRV

AGND

SS/EN

V

FB

V

CORE

VID4

VID3

8

VID3

VID4

VID2

VID1

VID0

C3

1µF

12V

7

6

5

4

3

2

1

11

12

13

14

15

16

9

10

L2,

1µH

Q4*

SCR

2N6504

R3

10k

Ω

C

SS

0.1µF

PWRGD

* Q4 optional OVP crowbar

Plastic SOIC

16-pin

D

LX1669

NOTE: For current data & package dimensions, visit our web site: http://www.linfinity.com.