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ISL6608

Synchronous Rectified MOSFET Driver

with Pre-Biased Load Startup Capability

The ISL6608 is a high frequency, MOSFET driver optimized

to drive two N-Channel power MOSFETs in a synchronous-

rectified buck converter topology. This driver combined with

an Intersil HIP63xx or ISL65xx Multi-Phase Buck PWM

controller forms a complete single-stage core-voltage

regulator solution with high efficiency performance at high

switching frequency for advanced microprocessors.

The IC is biased by a single low voltage supply (5V) and

minimizes gate drive losses due to MOSFET gate charge at

high switching frequency applications. Each driver is capable

of driving a 3000pF load with a low propagation delay and

less than 10ns transition time. This product implements

bootstrapping on the upper gate with an internal bootstrap

Schottky diode, reducing implementation cost, complexity,

and allowing the use of higher performance, cost effective

N-Channel MOSFETs. Adaptive shoot-through protection is

integrated to prevent both MOSFETs from conducting

simultaneously.

The ISL6608 features 4A sink current for the lower gate

driver, which is capable of holding the lower MOSFET gate

during the Phase node rising edge to prevent shoot-through

power loss caused by the high dv/dt of the Phase node.

The ISL6608 also features a Three-State PWM input which,

working together with Intersil multi-phase PWM controllers,

will prevent a negative transient on the output voltage when

the output is shut down. This feature eliminates the Schottky

diode that is usually seen in a microprocessor power system

for protecting the microprocessor from reversed output

voltage events.

A diode emulation feature is integrated in the ISL6608 to

enhance converter efficiency at light load conditions. Diode

emulation also prevents a negative transient when starting

up with a pre-biased voltage on the output. When diode

emulation is enabled, the driver allows discontinuous

conduction mode by detecting when the inductor current

reaches zero and subsequently turns off the low side

MOSFET, which prevents the output from sinking current

and producing a negative transient on a pre-biased output

(see Figures 6 and 7 on page 7).

Features

• Dual MOSFET Drives for Synchronous Rectified Bridge

• Adaptive Shoot-Through Protection

•0.5

Ω On-Resistance and 4A Sink Current Capability

• Supports High Switching Frequency up to 2MHz

- Fast Output Rise/Fall Time and Low Propagation Delay

• Three-State PWM Input for Power Stage Shutdown

• Internal Bootstrap Schottky Diode

• Low Bias Supply Current (5V, 80µA)

• Diode Emulation for Enhanced Light Load Efficiency and

Pre-Biased Startup Applications

• VCC POR (Power-On-Reset) Feature Integrated

• Low Three-State Shutdown Holdoff Time (Typically 160ns)

• Pin-to-Pin Compatible with ISL6605

• QFN Package:

- Compliant to JEDEC PUB95 MO-220

QFN - Quad Flat No Leads - Package Outline

- Near Chip Scale Package footprint, which improves

PCB efficiency and has a thinner profile

• Pb-free Available as an Option

Applications

• Core Voltage Supplies for FPGAs and PowerPC

Microprocessors

• Point-Of-Load Modules with Pre-Biased Start-Up

Requirements

• High Frequency and High Current DC-DC Converters

Related Literature

• Technical Brief TB363 “Guidelines for Handling and

Processing Moisture Sensitive Surface Mount Devices”

Data Sheet

March 2004

FN9140.1

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

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Copyright © Intersil Americas Inc. 2004. All Rights Reserved

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