High Efficiency, Main Power Supply Controllers for Notebook Computers

General Description

The RT8205A/B/C dual step-down, switch-mode power supply controller generates logic-supply voltages in battery-powered systems. The RT8205A/B/C includes two pulse-width modulation (PWM) controllers fixed at 5V/3.3V or adjustable from 2V to 5.5V. An alternative LGATE1

output LG1_CP can be used for external charge pump (RT8205B). And an optional external charge pump can be monitored through SECFB (RT8205C). 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 RT8205A/B/C includes on-board power-up sequencing, the power-good output, internal soft start, and internal soft-discharge output that prevents negative voltages on shutdown.

Features

Wide Input Voltage Range 6V to 25V

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

Alternative LGATE1 Output (LG1_CP) acts as Clock for Charge Pump (RT8205B)

Secondary Feedback Input Maintains Charge Pump Voltage (RT8205C)

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