The RT9221 integrates a PWM controller and two low-dropout linear regulators into a single chip. The PWM controller provides the CPU core voltage controlled by a 5-bit DAC and the linear section regulates power for GTL bus, clock driver or other circuits on motherboards. The PWM controller provides an adjustable Intel-compatible 1.3V~3.5V output voltage. The synchronous N-MOSFET driver with 200 KHz switching frequency optimizes the efficiency, device size, and cost built-in overvoltage and current-limiting protection prevent the CPU from damage. Power-good signal is sent when the core voltage is within 10% of the setting point.