The HIP6021 provides the power control and protection for four output voltages in high-performance, graphics intensive microprocessor and computer applications. The IC integrates a voltage-mode PWM controller and three linear controllers, as well as the monitoring and protection functions into a 28-pin SOIC package. The PWM controller regulates the microprocessor core voltage with a synchronous-rectified buck converter. The linear controllers regulate the computer system's AGP 1.5V or 3.3V bus power, the 1.5V GTL bus power, and the 1.8V power for the North/South Bridge core voltage and/or cache memory circuits. The HIP6021 includes an Intel-compatible, TTL 5-input digital-to-analog converter (DAC) that adjusts the core PWM output voltage from 1.3VDC to 2.05VDC in 0.05V steps and from 2.1VDC to 3.5VDC in 0.1V increments. The precision reference and voltage-mode control provide 1% static regulation. The AGP bus power linear controller's output (VOUT2) is user-selectable, through a TTL-compatible signal applied at the SELECT pin, for levels of 1.5V or 3.3V with 3% accuracy. Based on the status of the FIX pin, the other two linear regulators provide either fixed output voltages of 1.5V3% (VOUT3) and 1.8V3% (VOUT4), or user-adjustable by means of an external resistor divider. All linear controllers can employ either N-channel MOSFETs or bipolar NPNs for the pass transistor. The HIP6021 monitors all the output voltages. A single Power Good signal is issued when the core is within 10% of the DAC setting and all other outputs are above their undervoltage levels. Additional built-in over-voltage protection for the core output uses the lower MOSFET to prevent output voltages above 115% of the DAC setting. The PWM controller's over-current function monitors the output current by using the voltage drop across the upper MOSFET's rDS(ON).