High-Efficiency, Quad Output, Main Power-Supply Controllers for Notebook Computers

The RT8203 dual step-down, Switch Mode Power Supply (SMPS) controllers generate logic-supply voltages in battery-powered systems. The RT8203 include two pulse-width modulation (PWM) controllers, adjustable from 2V to 5.5V or fixed at 5V and 3.3V. These devices feature two linear regulators providing 5V and 3.3V always-on outputs. Each linear regulator provides up to 100mA output current with automatic linear regulator bootstrapping to the main SMPS outputs. The RT8203 include on-board power-up sequencing, a power good (PGOOD) output, internal soft-start, and soft-shutdown output discharge that prevents negative voltages on shutdown. RichTek's proprietary Mach-PWM^TM "instant-on" response, constant on-time PWM control scheme operates without sense resistors and provides 100ns response to load transients while maintaining a relatively constant switching frequency. The unique ultrasonic mode maintains the switching frequency above 25kHz, which eliminates noise in audio applications. Other features include diode-emulation, which maximizes efficiency in light-load applications, and fixed-frequency PWM mode, which reduces RF interference in sensitive applications. The RT8203 provides a pin-selectable switching frequency, allowing either 200kHz/300kHz or 400kHz/500kHz operation of the 5V/3.3V SMPSs, respectively. The RT8203 is available in SSOP-28 package.