High Efficiency, Main Power Supply Controller for Notebook Computers

The RT8206L/M dual step-down, Switch-Mode Power- Supply (SMPS) controller generates logic-supply voltages in battery-powered systems. The RT8206L/M includes two Pulse-Width Modulation (PWM) controllers fixed at 5V/ 3.3V or adjustable from 2V to 5.5V. An optional external charge pump can be monitored through SECFB (RT8206L). This device also features a linear regulator providing a fixed 5V output. The linear regulator provides up to 70mA output current with automatic linear regulator bootstrapping to the BYP input. The RT8206L/M includes on-board power-up sequencing, the power good outputs, internal soft-start, and internal soft-discharge output that prevents negative voltages on shutdown. A 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 Mode (DEM), which maximizes efficiency in light-load applications, and fixed frequency PWM mode, which reduces RF interference in sensitive application.