AN701

AN701 Vishay Siliconix Designing High-Frequency DC-to-DC Converters With the Si9114A Switchmode Controller INTRODUCTION Vishay Siliconix’s Si9100 monolithic switchmode PWM controller established the standard for low-power, highefficiency dc-to-dc converters. This versatile device integrates a number of useful features, including a power MOSFET, high-voltage start circuitry, and low power consumption. The Si9114A controller pushes the limits for high-frequency power conversion by further reducing delay times and adding additional features. As a result, dc-to-dc converters can be designed for frequencies up to 1 MHz with simple PWM topologies instead of the complex resonant ones. S reduce the size of energy storage components S increase reliability by using ceramic capacitors S produce an all-surface-mount assembly solution S lower system costs S simplify the implementation of a distributed power architecture. Traditionally, distributed power has been regarded as costly and impractical to implement due to the high cost of local power conversion and the perceived complexity of resonant power supplies. But these decision criteria are now being changed by the availability of small-outline control ICs, LITTLE FOOTr MOSFETs, ceramic capacitors, and new magnetic components. The Si9114A uses constant frequency current mode control. By increasing the conversion frequency, power supply designers will be able to: FB 5 COMP 6 Error Amplifier CURRENT SENSE 13 SYNC 10 ROSC 8 COSC 9...