SI786

Si786 Vishay Siliconix Dual-Output Power-Supply Controller FEATURES D D D D Fixed 5-V and 3.3-V Step-down Converters Less than 500-mA Quiescent Current per Converter 25-mA Shutdown Current 5.5-V to 30-V Operating Range DESCRIPTION The Si786 Dual Controller for Portable Computer Power Conversion is pin and functionally compatible with the MAX786 dual-output power supply controller for notebook computers. The device is designed as a drop-in replacement for that circuit. The circuit is a system level integration of two step-down controllers, micropower 5-V and 3.3-V linear regulators, and two comparators. The controllers perform high efficiency conversion of the battery pack energy (typically 12 V) or the output of an ac to dc wall converter (typically 18-V to 24-V dc) to 5-V and 3.3-V system supply voltages. The micropower linear regulator can be used to keep power management and back-up circuitry alive during the shutdown of the step-down converters. The comparators can be biased at any voltage between 2.7 V and the input voltage, simplifying battery monitoring or providing sufficient voltage to enhance the gate of a low on-resistance n-channel FET used in switching power to different zones in the system. A complete power conversion and management system can be implemented with the Si786 Dual Controller for Portable Computer Power Conversion, an inexpensive linear regulator, the Si9140 SMP Controller for High Performance Processor Power Supplies, five Si4410 n-channel Trench...