1

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FN6901.0

ISL6420B

Advanced Single Synchronous Buck

Pulse-Width Modulation (PWM) Controller

The ISL6420B simplifies the implementation of a complete

control and protection scheme for a high-performance

DC/DC buck converter. It is designed to drive N-channel

MOSFETs in a synchronous rectified buck topology, the

ISL6420B integrates control, output adjustment, monitoring

and protection functions into a single package. Additionally,

the IC features an external reference voltage tracking mode

for externally referenced buck converter applications and

DDR termination supplies, as well as a voltage margining

mode for system testing in networking DC/DC converter

applications.

The ISL6420B provides simple, single feedback loop,

voltage mode control with fast transient response. The

output voltage of the converter can be precisely regulated to

as low as 0.6V.

The operating frequency is fully adjustable from 100kHz to

1.4MHz. High frequency operation offers cost and space

savings.

The error amplifier features a 15MHz gain-bandwidth

product and 6V/µs slew rate that enables high converter

bandwidth for fast transient response. The PWM duty cycle

ranges from 0% to 100% in transient conditions. Selecting

the capacitor value from the ENSS pin to ground sets a fully

adjustable PWM soft-start. Pulling the ENSS pin LOW

disables the controller.

The ISL6420B monitors the output voltage and generates a

PGOOD (power good) signal when soft-start sequence is

complete and the output is within regulation. A built-in

overvoltage protection circuit prevents the output voltage

from going above typically 115% of the set point. Protection

from overcurrent conditions is provided by monitoring the

appropriately. This approach simplifies the implementation

and improves efficiency by eliminating the need for a current

sensing resistor.

Features

• Operates From:

- 4.5V to 5.5V Input

- 5.5V to 28V Input

• 0.6V Internal Reference Voltage

- ±2.0% Reference Accuracy

• Resistor-Selectable Switching Frequency

- 100kHz to 1.4MHz

• Voltage Margining and External Reference Tracking

Modes

• Output Can Sink or Source Current

• Lossless, Programmable Overcurrent Protection

• Programmable Soft-Start

• Drives N-Channel MOSFETs

• Simple Single-Loop Control Design

- Voltage-Mode PWM Control

• Fast Transient Response

- High-Bandwidth Error Amplifier

- Full 0% to 100% Duty Cycle

• Extensive Circuit Protection Functions

- PGOOD, Overvoltage, Overcurrent, Shutdown

• Diode Emulation during Startup for Pre-Biased Load

Applications

• Offered in 20 Ld QFN and QSOP Packages

• QFN (4x4) Package

- QFN compliant to JEDEC PUB95 MO-220 QFN - Quad

Flat No Leads - Product Outline

- QFN Near Chip Scale Package Footprint; Improves

PCB Efficiency, Thinner in Profile

• Pb-Free (RoHS Compliant)

Applications

• Power Supplies for Microprocessors/ASICs

- Embedded Controllers

- DSP and Core Processors

- DDR SDRAM Bus Termination

• Ethernet Routers and Switchers

• High-Power DC/DC Regulators

• Distributed DC/DC Power Architecture

• Personal Computer Peripherals

• Externally Referenced Buck Converters

Data Sheet

CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.

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Copyright © Intersil Americas Inc. 2009. All Rights Reserved

All other trademarks mentioned are the property of their respective owners.

April 27, 2009