A system and method is disclosed that provides a digital self-adjusting power supply for semiconductor digital circuits. The power supply provides a substantially constant minimum supply voltage with regard to process corner, junction temperature, external voltage source, load variation, and operating frequency. The system comprises a slack time detector, a voltage adjuster, and a digital pulse width modulation (PWM) modulator. The system supplies a minimum required voltage without the used of a band gap or reference voltage. A finite state machine is also used to minimize oscillations introduced by start-up, load transients, frequency changes, and the like, thereby eliminating the need for a proportional integrator differentiator (PID) circuit.