RT9231A

The RT9231A is a 4-in-one power controller optimized for high-performance microprocessor and computer applications. The IC integrates a PWM controller, triple linear controller as well as monitoring and protection functions into a 28-pin SOP package. The PWM controller regulates the microprocessor core voltage with a synchronous buck converter. The first linear controller supplies the computer system's AGP 1.5V or 3.3V bus power. The second linear controller provides power for the 1.5V GTL bus and the 3rd linear controller provides 1.8V power for the North/South Bridge core voltage and/or cache memory circuits.

The RT9231A features an Intel-compatible, TTL 5-bit programmable DAC that adjusts the core voltage from 2.1V to 3.5V in 0.1V increments and from 1.3V to 2.05V in 0.05V steps. The 5-bit DAC has a typical ±1% tolerance. The first linear controller is userselectable for output level of 1.5V and 3.3V with ±2.5% accuracy. The other two linear controllers provide fixed output voltages of 1.5V ±3% and 1.8V ±3%. All the three linear controllers drive external NMOSFET or NPNs bipolar for the pass transistor.

The RT9231A monitors all the output voltages. A power-good signal is issued when the core voltage is within ±10% of the DAC setting and the other levels are above their under-voltage levels. Additional buildin over-voltage protection for the core output uses the lower MOSFET to prevent output voltage above 115% of the DAC setting. The PWM over-current function monitors the output current using the voltage drop across the MOSFET's R_DS(ON), which eliminates the need for a current sensing resistor.