The small-signal dynamic characteristics of the current sharing loop and the limit-cycle oscillation condition of the digital multi-phase DC-DC converter were analyzed. A digital current sharing technology based on average current was proposed, and a multi-phase DC-DC digital controller was designed. A current sharing control circuit and a digital pulse width modulator (DPWM) based on the synchronous design were presented to achieve current balancing and interleave operation. The multi-phase DC-DC digital controller chip was designed in a 0.18μm CMOS process. The simulation results showed that under 10 A~20 A load transient, the overshoot/undershoot voltage was within 20 mV, the switching frequency was adjustable from 0.5 MHz to 2 MHz, and the current sharing error was reduced from 20.8% to less than 5%.