High Efficiency, Main Power Supply Controller for Notebook Computers

The RT8239A/B/C is a dual step down, Switch Mode Power Supply (SMPS) controller which generates logic supply voltages for battery powered systems. It includes two Pulse Width Modulation (PWM) controllers adjustable from 2V to 5.5V and also two fixed 5V/3.3V linear regulators. One of the controllers (LDO5) provides automatic switch over to the BYP1 input connected to the main SMPS1 output for maximized efficiency. An optional external charge pump can be monitored through SECFB (RT8239B/C). Other features include on board power up sequencing, a power good output, internal soft-start, and a soft discharge output that prevents negative voltage during shutdown.
A constant on-time PWM control scheme operates without sense resistors and assures fast load transient response while maintaining nearly constant switching frequency. To eliminate noise in audio applications, an ultrasonic mode is included, which maintains the switching frequency above 25kHz. Moreover, a diode emulation mode maximizes efficiency for light load applications. The SMPS1/SMPS2 switching frequency can be adjustable from 200kHz/233kHz to 400kHz/466kHz respectively.
The RT8239A/B/C is available in a WQFN-20L 3x3 package, and operates over an extended temperature range from -40°C to 85°C.