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FN9151.4

ISL6420

Advanced Single Synchronous Buck

Pulse-Width Modulation (PWM) Controller

The ISL6420 makes simple work out of implementing a

complete control and protection scheme for a high-

performance DC/DC buck converter. Designed to drive

N-channel MOSFETs in a synchronous rectified buck

topology, the ISL6420 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 ISL6420 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, with a maximum tolerance of ±1.0% over

temperature and line voltage variations.

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 ISL6420 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 16V Input

• Excellent Output Voltage Regulation

- 0.6V Internal Reference

- ±1.0% Reference Accuracy Over Line and Temperature

• 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

• 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

• Also Available in QSOP Package

• Pb-Free Plus Anneal Available (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

July 18, 2005

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

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