LX1671
I N T E G R A T E D
P R O D U C T S
Multiple Output LoadSHARE™ PWM
P
RODUCTION
D
ATA
S
HEET
DESCRIPTION
KEY FEATURES
WWW .
Microsemi
.C
OM
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 Sharing
†
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
MOSFET R
DS(ON)
impedance, monitors
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,
the LoadSHARE
TM
topology can be
programmed via inductor ESR selection.
There are three other methods that can
also be used with LoadSHARE
TM
. These
other methods are presented in the theory
of operation section of this data sheet.
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
IMPORTANT:
For the most current data, consult
MICROSEMI’s
website:
http://www.microsemi.com
LoadSHARE is a Trademark of Microsemi Corporation
PRODUCT HIGHLIGHT
DDR Term ination
Refer to Typical
Application for
com plete circuit.
12V
5V
3.3V
I/O
LX1671
M em ory Core
....
Core
Graphics
Controller
M em ory Bus
DDR M em ory
LX1671
LX1671
T
A
(°C)
0 to 70
Copyright
©
2000
Rev. 1.0a, 2004-06-14
PACKAGE ORDER INFO
Plastic TSSOP
Plastic MLPQ
PW
38-Pin
LQ
38-Pin
LX1671-CPW
LX1671-CLQ
Note: Available in Tape & Reel. Append the letters “TR” to the part number (i.e. LX1671CPWTR)
Microsemi
Integrated Products, Power Management
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
MICROSEMI [ MICROSEMI CORPORATION ]
