A power management circuit included in a computer system regulates a voltage level of a power supply node used by other circuits in the computer system. The power management circuit includes a control circuit and multiple phase circuits coupled to the regulated power supply node via corresponding inductors. The control circuit selectively activates particular ones of the multiple phase circuits allowing them source respective currents to the regulated power supply node. The control circuit also selectively activates particular ones of other phase circuits that are external to the power management circuit and coupled to the regulated power supply node via their own corresponding inductors. Once activated, the external phase circuits source respective currents to the regulated power supply node via their corresponding inductors.