Microsemi

Integrated Products, Power Management

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

Page 1

Copyright

© 2000

Rev. 1.2b, 2006-02-13

LX1671

Multiple Output LoadSHARE™ PWM

TM

®

DESCRIPTION

The LX1671 is a highly integrated

power supply controller IC featuring

three PWM switching regulator stages

with an additional onboard linear

regulator driver.

Two of the constant frequency

voltage-mode PWM phases can be

easily configured for a single Bi-Phase

high current output or two in-

dependently regulated outputs. Each

phase

incorporates

a

fully

pro-

grammable soft-start sequence. This

versatility yields either three or four

independently regulated outputs with

full power sequencing capability giving

system

designers

the

ultimate

flexibility in power supply design.

In Bi-Phase operation, the high

current (>30A) output can utilize

different supply rails allowing Forced

Current

from

different

sources. Power loss and noise, due to

the ESR of the input capacitors, are

minimized by operating each PWM

output 180

° out of phase. This

architecture also minimizes capacitor

requirements while maximizing re-

gulator response.

The additional outputs are capable of

supplying up to 5A (Linear Regulator

Driver) and 15A (Switching Regulator)

for I/O, memory, termination, and other

supplies surrounding today’s micro-

processor designs.

Each

PWM regulator

output

is

programmed via a simple voltage-divider

network.

The

LX1671,

utilizing

current limit conditions, in each PWM

phase, without the use of expensive

current sense resistors.

The LX1671 was designed to give

design engineers maximum flexibility

with respect to the MOSFET supply.

Each phase can utilize different supply

voltages for efficient use of available

supply rails.

Additionally, when two

phases are configured in Bi-Phase output,

programmed via inductor ESR selection.

There are three other methods that can

other methods are presented in the theory

of operation section of this data sheet.

IMPORTANT:

For the most current data, consult MICROSEMI’s website: http://www.microsemi.com

LoadSHARE is a Trademark of Microsemi Corporation

Protected by US Patents: 6,285,571 & 6,292,378

KEY FEATUR ES

Up to Four Independently

Regulated Outputs

Outputs As Low As 0.8V

Generated From An Internal 1%

Reference

Multiphase High Current Output

Reduces Required Capacitance

Integrated High Current MOSFET

Drivers

300kHz High Frequency Operation

Minimizes External Component

Requirements

Independent Phase Programmable

Soft-Start and Power Sequencing

Adjustable Linear Regulator Driver

Output

No current-sense resistors

DDR Termination Compliant

APPLICATIONS/BENEFITS

Multi-Output Power Supplies

Video Card Power Supplies

PC Peripherals

Portable PC Processor and I/O

Supply

PRODUCT H I GHLIGHT

Memory Bus

....

DDR Termination

Memory Core

12V

3.3V

I/O

Graphics

Controller

DDR Memory

LX1671

Refer to Typical

Application for

complete circuit.

5V

Core

PACKAGE ORDER INFO

PW

Plastic TSSOP

38-Pin

LQ

Plastic MLPQ

38-Pin

RoHS Compliant / Pb-free Transition DC: 0518

RoHS Compliant / Pb-free Transition DC: 0512

0 to 70

LX1671CPW

LX1671CLQ

Note: Available in Tape & Reel. Append the letters “TR” to the part number (i.e. LX1671CPW-TR)