This paper presents a digital sliding mode controller, based on the technique of adaptive supply voltage regulation, for dc-dc switching converter. The using of adaptive supply voltage regulator could save power consumption by reducing the voltage of operating frequency of control circuit. A design example and simulation results are presented for a digital sliding mode controller used to control 3.3V to 1.2V buck converter with less than 20mV ripples, in the switching frequency of 520kHz. The digital controller dissipation is 0.5mW at 1.2V regulated output.