In this paper, a controller for a multiphase interleaved buck converter with alternate phase-shedding is realized. With phase-shedding control, the efficiency at low load condition is improved by turning-on appropriate number of phase(s), but the temperature on the active phase(s) is higher than the off phase(s) that cause the temperature unevenly distribution. To solve this problem, the alternate phase-shedding is implemented in the proposed controller. The phases take turns to provide the load current at low load condition to distribute power to each phase and share the same load as well as improve reliability. The proposed controller would implement interleaved control regardless the number of active phases. In addition, taking advantage of the application of high step-down ratio, the proposed control structure that input current is sensed to control each phase is adopted. The number of components and pins of controller can be reduced. This chip is fabricated with TSMC 0.25um CMOS high voltage mixed signal general purpose process and is tested with an input voltage of 12 V, output voltage of 1.2 V, and output power of 72 W three-phase buck converter to verify the feasibility.