intersil ISL6431 DATA SHEET
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ISL6431
Data Sh eet June 200 1
Advanced Pulse-Width Modulation (PWM)
Controller for Home Gateways
The ISL6431 is a high efficiency, fixed frequency,
synchronousbuck PWM controller. Itis designed for use in
applicationsthat convert5V 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 D C-DC
stepdownconverter.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, voltagemode control with fast transient response. The output
voltagecan be precisely regulated to as low as 0.8V,with a
maximum t olerance of ±1.5% over temperatureand l ine
voltagevariations. 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/µs slew rate which enables high converter
bandwidthfor fast transient performance. The resulting
PWM duty cycles range from 0% to 100%.
Protection from overcurrent conditions is provided by
monitoringthe r
DS(ON)
operation appropriately. This approach simplifies the
implementation and improves efficiency by eliminating the
need for a current sense r esistor.
of the upper MOSFET toinhibit PWM
File Number 9018
Features
• Operates from +5V Input
•0.8VtoV
Output Range
IN
- 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
- InternalSoft Start
- 8 Lead SOIC Package
• High Conversion Efficiency
• Synchronous/Standard Buck Configuration
Applications
• Cable Modems, Set TopBoxes, and DSL Modems
• DSP and Core CommunicationsProcessor Supplies
• Power Supplies for Microprocessors and Embedded
Controllers
• Memory Supplies
• Personal Computer Per ipherals
• Industrial Power Supplies
Ordering Information
TEMP.RANGE
PART NUMBER
ISL6431CB 0 to 70 8 Ld SOIC M8.15
ISL6431IB -40 to 85 8 Ld SOIC M8.15
ISL6431EVAL1 Evaluation Board
(oC) PACKAGE
1
PKG.
• 5V-Input DC-DC Regulators
• Low-Voltage Distributed Power Supplies
NO.
Pinout
1
BOOT
2
UGATE
3
GND
LGATE
4
CAUTION: These devices aresensitiveto electrostatic discharge;followproperIC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil andDesign is a trademark of Intersil AmericasInc.
Copyright © Intersil Americas Inc. 2001, All Rights Reserved
8
PHASE
COMP/OCSET
7
6
FB
5
VCC
Block Diagram
ISL6431
V
CC
0.8V
FB
COMP/OCSET
Typical Application
+
-
20µA
SAMPLE
AND
HOLD
ERROR
AMP
V
CC
+
-
COMPARATOR
+
-
OC
PWM
COMPARATOR
+
-
OSCILLATOR
FIXED 300kHz
POR AND
SOFTSTART
PWM
INHIBIT
GATE
CONTROL
LOGIC
GND
BOOT
UGATE
PHASE
VCC
LGATE
R
1
R
2
C
1
R
3
C
3
COMP/OCSET
C
2
ISL6431
7
63
FB
5
VCC
GND
1
2
8
4
C
4
BOOT
UGATE
PHASE
LGATE
C
D
BOOT
C
6
L
OUT
R
4
5
+VO=0.8toV
C
7
IN
2
ISL6431
Absolute M aximum Ratings Thermal Information
Supply Voltage, VCC................................+6.0V
Absolute Boot Voltage, V
Upper Driver Supply Voltage, V
Input, Output or I/O Voltage. . . . . . . . . . . GND -0.3V to VCC +0.3V
.......................+15.0V
BOOT
BOOT-VPHASE
...........+6.0V
ESDClassification.................................Class2
Operating Conditions
SupplyVoltage,VCC............................+5V±10%
AmbientTemperatureRange...................-40
JunctionTemperatureRange.................. -40
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operationofthe
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTE:
is measured with the component mountedon a low effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
1. θ
JA
o
Cto85oC
o
Cto125oC
Thermal Resistance (Typical, Note 1) θ
JA
(oC/W)
SOICPackage............................. 100
MaximumJunctionTemperature...................... 150
MaximumStorageTemperatureRange..........-65
o
Cto150oC
Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . 300
(SOIC - Lead Tips Only)
o
C
o
C
Electrical Specifications Recommended OperatingConditions, Unless Otherwise Noted V
=5.0V±5% and TA=25oC
CC
PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNITS
VCC SUPPLY CURRENT
NominalSupply I
VCC
ISL6431CB; UGATE and LGATE Open - 3.2 - mA
ISL6431IB; UGATE and LGATE Open 2.5 3.2 3.8 mA
POWER-ON RESET
Rising VCC POR Threshold POR ISL6431CB - 4.30 - V
ISL6431IB 4.17 4.30 4.50 V
VCC POR Threshold
Hysteresis
ISL6431CB - 0.20 - V
ISL6431IB 0.01 0.20 0.85 V
OSCILLATOR
Frequency f
OSC
ISL6431CB; VCC = 5V - 300 - kHz
ISL6431IB; VCC = 5V 230 300 340 kHz
Ramp Amplitude ∆V
OSC
ISL6431CB - 1.5 - V
ISL6431IB - 1.5 - V
REFERENCE
Reference Voltage Tolerance ISL6431CB - - 1.5 %
ISL6431IB - - 1.5 %
NominalReferenceVoltage V
REF
ISL6431CB - 0.800 - V
ISL6431IB - 0.800 - V
ERROR AMPLIFIER
DC Gain ISL6431CB - 82 - dB
ISL6431IB - 82 - dB
Gain-BandwidthProduct GBWP ISL6431CB 14 - - MHz
ISL6431IB 14 - - MHz
Slew Rate SR ISL6431CB; COMP = 10pF - 8.0 - V/µs
ISL6431IB; COMP = 10pF 4.5 8.0 9.2 V/µs
GATE DRIVERS
UpperGate Source Current I
UpperGate Sink Current I
UGATE-SRC
UGATE-SNK
ISL6431CB;V
ISL6431IB; V
BOOT-VPHASE
BOOT-VPHASE
ISL6431CB - 1.0 - A
=5V,V
=5V,V
=4V - 1.0 - A
UGATE
=4V - 1.0 - A
UGATE
ISL6431IB - 1.0 - A
LowerGate Source Current I
LGATE-SRC
ISL6431CB; VCC=5V,V
ISL6431IB; V
CC
=5V,V
=4V - 1.0 - A
LGATE
=4V - 1.0 - A
LGATE
P-P
P-P
3
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