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 modulations (PWM) controllers fixed at 5V/ 3.3V or adjustable from 2V to 5.5V. An alternative LGATE1 output LG1_CP can be used for an 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. A constant on-time PWM control scheme operates without a sense resistor and provides a 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 applications.
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
