Tiny PWM Controllers Help Implement Low-Cost Supplies

Targeted at PC manufacturers and makers of embedded and industrial CPU boards as well as users of high-performance memory and multimedia processors, the LX1681/82 family of monolithic PWM controller ICs are designed for implementing low-cost buck regulator supplies with a minimal of external components. Typical conversions are from 5V to 3.3V, 5V to 2.5V, or 5V to 1.8V for applications on computer motherboards, hard disk drives, graphics cards and general-purpose dc-to-dc converters. Two versions are available: LX1681 is for standard buck configurations, implemented with a standard n-channel FET and Schottky diode; and LX1682 offers greater efficiency in synchronous rectifier configurations driving a pair of FETs. Both devices are supplied in small 8-pin surface-mount packages and feature soft-start, hiccup-mode current limiting, and chip-enable functions.