
1
TM
File Number
9018
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
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Intersil and Design is a trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2001, All Rights Reserved
ISL6431
Advanced Pulse-Width Modulation (PWM)
Controller for Home Gateways
The ISL6431 is a high efficiency, fixed frequency,
synchronous buck PWM controller. It is designed for use in
applications that convert 5V to lower distributed voltages
required for set-top box, cable modem, DSL modem and
residential home gateway core processor, memory and
peripheral power supplies.
This device makes simple work out of implementing a
complete control and protection scheme for a DC-DC
stepdown converter. Designed to drive N-channel MOSFETs
in a synchronous buck topology, the ISL6431 integrates the
control, output adjustment, monitoring and protection
functions into a single 8-pin package.
The ISL6431 provides simple, single feedback loop, voltage-
mode control with fast transient response. The output
voltage can be precisely regulated to as low as 0.8V, with a
maximum tolerance of ±1.5% over temperature and line
voltage variations. A fixed frequency oscillator reduces
design complexity, while balancing typical application cost
and efficiency.
The error amplifier features a 15MHz gain-bandwidth
product and 6V/
μ
s slew rate which enables high converter
bandwidth for fast transient performance. The resulting
PWM duty cycles range from 0% to 100%.
Protection from overcurrent conditions is provided by
monitoring the r
DS(ON)
of the upper MOSFET to inhibit PWM
operation appropriately. This approach simplifies the
implementation and improves efficiency by eliminating the
need for a current sense resistor.
Features
Operates from +5V Input
0.8V to V
IN
Output Range
- 0.8V Internal Reference
- ±1.5% Over Line Voltage and Temperature
Drives N-Channel MOSFETs
Simple Single-Loop Control Design
- Voltage-Mode PWM Control
Fast Transient Response
Lossless, Programmable Overcurrent Protection
- Uses Upper MOSFET’s r
DS(ON)
Small Converter Size
- 300kHz Fixed Frequency Oscillator
- Internal Soft Start
- 8 Lead SOIC Package
High Conversion Efficiency
Synchronous/Standard Buck Configuration
Applications
Cable Modems, Set Top Boxes, and DSL Modems
DSP and Core Communications Processor Supplies
Power Supplies for Microprocessors and Embedded
Controllers
Memory Supplies
Personal Computer Peripherals
Industrial Power Supplies
5V-Input DC-DC Regulators
Low-Voltage Distributed Power Supplies
Pinout
Ordering Information
PART NUMBER
TEMP.RANGE
(
o
C)
PACKAGE
PKG.
NO.
ISL6431CB
0 to 70
8 Ld SOIC
M8.15
ISL6431IB
-40 to 85
8 Ld SOIC
M8.15
ISL6431EVAL1
Evaluation Board
5
6
8
7
4
3
2
1
UGATE
GND
PHASE
FB
VCC
COMP/OCSET
BOOT
LGATE
Data Sheet
June 2001