General Description

The RT8223A/B dual step-down, switch-mode power supply controller generates logic-supply voltages in battery-powered systems. The RT8223A/B includes two pulse-width modulation (PWM) controllers fixed at 5V/3.3V or adjustable from 2V to 5.5V. This device also features 2 linear regulators providing fixed 5V and 3.3V outputs. The linear regulator each provides up to 70mA output current with automatic linear-regulator bootstrapping to the PWM outputs. The RT8223A/B includes on-board power-up sequencing, the power good output, internal soft start, and internal soft-discharge output that prevents negative voltages on shutdown.

A constant on-time PWM control scheme operates without sense resistor 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.

Features

• Wide Input Voltage Range 6V to 25V

• Dual Fixed 5V/3.3V Outputs or Adjustable from 2V to 5.5V, 1.5% Accuracy

• Fixed 3.3V and 5V LDO Output : 70mA

• 2V Reference Voltage ±1% : 50μA

• Constant ON-Time Control with 100ns Load Step Response

• Frequency Selectable via TONSEL Setting

• RDS(ON) Current Sensing and Programmable Current Limit combined with Enable Control

• Selectable PWM, DEM, or Ultrasonic Mode

• Internal Soft-Start and Soft-Discharge

• High Efficiency up to 97%

• 5mW Quiescent Power Dissipation

• Thermal Shutdown

• RoHS Compliant and Halogen Free

Applications

• Notebook and Sub-Notebook Computers

• 3-Cell and 4-Cell Li+ Battery-Powered Devices