Microsemi
Integrated Products, Power Management
11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570
Page 1
Copyright
2000
Rev. 0.5i, 2002-07-17
W
M
.
C
LX1671
Multiple Output LoadSHARE PWM
P
RELIMINARY
I N T E G R A T E D P R O D U C T S
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
grammable soft-start sequence. This
versatility yields either three or four
independently regulated outputs with
full power sequencing capability giving
system
designers
flexibility in power supply design.
In Bi-Phase operation, the high
current (>30A) output can utilize
different supply rails allowing Forced
Current
Sharing
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.
a
fully
pro-
the
ultimate
from
different
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
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.
LX1671,
utilizing
IMPORTANT:
For the most current data, consult
MICROSEMI
’s website:
http://www.microsemi.com
LoadSHARE is a Trademark of Microsemi Corporation
KEY FEATURES
!
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 HIGHLIGHT
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
38-Pin
LX1671-CPW
T
A
(
°
C)
Plastic TSSOP
LQ
Plastic MLPQ
38-Pin
LX1671-CLQ
0 to 70
L
X
1
6
7
1