An example phase interpolator includes: a ring oscillator having a plurality of delay stages and a plurality of injection switches, each of the plurality of injection switches responsive to a differential reference clock signal and a first differential control signal; a supply control circuit configured to provide a regulated supply voltage to the ring oscillator in response to a first component of a second differential control signal; and a ground control circuit configured to provide a regulated ground voltage to the ring oscillator in response to a second component of the second differential control signal.