RT9238

The RT9238 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 AGTL+ 1.2V bus power. The second linear controller provides power for the 1.5V AGP bus and the 3rd linear controller provides 1.8V power for the chipset core voltage and/or cache memory circuits.

The RT9238 features an Intel VRM8.5 compatible,TTL 5-bit programmable DAC that adjusts the core voltage from 1.090V to 1.865V in 25mV steps. The 5-bit DAC has a typical ±1% tolerance. The linear regulators provide fixed output voltages of 1.2V (V_OUT2), 1.5V (V_OUT3) and 1.8V (V_OUT4) or useradjustable with an internal 1.265V reference. All the three linear regulators drive external N-MOSFET or NPNs bipolar for the pass transistor.

The RT9238 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.