
1
TM
File Number
9041
ISL6440A
Advanced PWM and Triple Linear Power
Controller for Gateway Applications
The ISL6440A provides the power control and protection for
four output voltages required by microprocessors used in
high-performance, graphics-intensive gateway applications.
The IC integrates a voltage-mode PWM controller and three
linear controllers, as well as the monitoring and protection
functions into a 28 lead SOIC package.
The synchronous rectified buck converter includes an Intel-
compatible, TTL five-input, digital-to-analog converter (DAC)
that adjusts the core PWM output voltage from 1.3V
DC
to
2.05V
DC
in 0.05V steps and from 2.1V
DC
to 3.5V
DC
in 0.1V
increments. The precision reference and voltage-mode
control provide
±
1% static regulation. A TTL-compatible
signal applied to the SELECT pin dictates which method of
control is used for the AGP bus power. A low state results in
linear control of the AGP bus to 1.5V, while a high state
transitions the output through a linearly controlled soft-start
to 3.3V, followed by full enhancement of the external
MOSFET to pass the input voltage. The other two linear
regulators provide fixed output voltages of 1.5V GTL bus
power and 1.8V power for the north/south bridge core and/or
cache memory. These levels are user-adjustable by means
of an external resistor divider and pulling the FIX pin low. All
linear controllers can employ either N-Channel MOSFETs or
bipolar NPNs for the pass transistor.
The ISL6440A monitors all the output voltages. A single
power good signal is issued when the core is within
±
10% of
the DAC setting and all other outputs are above their under-
voltage levels. Additional built-in overvoltage protection for
the core output uses the lower MOSFET to prevent output
voltages above 115% of the DAC setting. The PWM
controller’s overcurrent function monitors the output current
by using the voltage drop across the upper MOSFET’s
r
DS(ON)
.
Features
Provides four regulated voltages
- Microprocessor core, AGP bus, memory, and GTL bus
power
Drives N-Channel MOSFETs
Linear regulator drives compatible with both MOSFET and
bipolar series pass transistors
Fixed or externally resistor-adjustable linear outputs
Simple single-loop control design
- Voltage-mode PWM control
Fast PWM converter transient response
- High-bandwidth error amplifier
- Full 0–100% duty ratio
Excellent output voltage regulation
- Core PWM output:
±
1% over temperature
- Other outputs:
±
3% over temperature
TTL-compatible 5-bit DAC core output voltage selection
- Shutdown feature removed when all inputs high
- Wide range 1.3V
DC
to 3.5V
DC
Power-good output voltage monitor
Overvoltage and overcurrent fault monitors
- Switching regulator does not require extra current
Sensing element, uses upper MOSFET’s r
DS(ON)
Small converter size
- Constant frequency operation
- 200kHz free-running oscillator; programmable from
50kHz to over 1MHz
- Small external component count
Applications
Power regulation for gateway processors
Pinout
ISL6440A (SOIC)
TOP VIEW
Ordering Information
PART NUMBER
TEMP.
RANGE (
o
C)
PACKAGE
PKG.
NO.
ISL6440ACB
0 to 70
28 Ld SOIC
M28.3
DRIVE2
FIX
VID4
VID3
VSEN2
SELECT
SS
FAULT/RT
VSEN4
VCC
PGND
LGATE
PHASE
DRIVE3
COMP
GND
VAUX
DRIVE4
UGATE
PGOOD
VID2
SD
VSEN1
VSEN3
VID1
VID0
OCSET
FB
28
27
26
25
24
23
22
21
20
19
18
17
16
15
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Data Sheet
October 2001
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143
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Intersil (and design) is a trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2001. All Rights Reserved
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