DESCRIPTION

The LX1660 and LX1661 Are Monolithic Switching Regulator Controller

ICs designed to provide low-cost, high performance adjustable power supply for microprocessors and other applications requiring a fast transient response and a high degree of accuracy. They provide an adjustable synchronous Pulse Width Modulator output suitable for a power supply for Pentium® or other microprocessors.

Synchronous Rectifier Driver For CPU Core. The devices can drive dual MOSFETs resulting in typical efficiencies of 85 - 90, even with loads in excess of 10A. Synchronous shutdown results in increased efficiency in light load applications.

Short-Circuit Current Limiting Without Expensive Current Sense Resistors. The current sensing mechanism can use a PCB trace resistance or the parasitic resistance of the main inductor. For applications requiring a high degree of accuracy, a conventional sense resistor can be used.

Hiccup Mode Fault Protection. The hiccup mode is programmable and with pulse-by-pulse current limiting will help protect the power supply system and load in the even of a short circuit.

Ultra-Fast Transient Response Reduces System Cost. The fixed frequency modulated off-time architecture results in the fastest transient response for a given inductor. Adaptive voltage positioning (LX1661 only) requires fewer low-ESR capacitors to meet stringent transient over and under-shoot specifications.

KEY FEATURES

■ Designed To Drive A Synchronous Rectifier

Stage — Can Also Be Used In Non

Synchronous Applications

■ Soft-Start Capability

■ Hiccup-Mode Fault Protection

■ No Current-Sense Resistor Required For

Current Limiting

■ Modulated Constant Off-Time Control

Mechanism For Fast Transient Response And

Simple System Design

■ 2V, 0.5 Internal Voltage Reference Brought Out

APPLICATIONS

■ Pentium Processor Supplies

■ AMD-K6TM Supplies

■ Cyrix® 6x86TM Supplies

■ Voltage Regulator Modules

■ General Purpose DC:DC Supplies