The ADP3421 is a hysteretic dc-dc buck converter controller with two auxiliary linear regulator controllers. The ADP3421 provides a total power conversion control solution for a microprocessor by delivering the core, I/O, and clock voltages. The optimized low-voltage design is powered from the 3.3 V system supply and draws only 10 A maximum in shutdown. The main output voltage is set by a 5-bit VID code. To accommodate the transition time required by the newest processors for on-thefly VID changes, the ADP3421 features high-speed operation to allow a minimized inductor size that results in the fastest change of current to the output. To further allow for the minimum number of output capacitors to be used, the ADP3421 features active voltage positioning that can be optimally compensated to ensure a superior load transient response. The main output signal interfaces with the ADP3410 dual MOSFET driver, which is optimized for high speed and high efficiency for driving both the upper and lower (synchronous) MOSFETs of the buck converter.