This paper presents the VLSI design of highly efficient low voltage DC/DC converter for portable devices. All active devices are integrated on a single chip using a standard 0.65$mu extrm{m}$ CMOS process. The converter operates at the switching frequency of 1MHz for reducing the size of passive elements and uses a ZVS for minimizing the switching loss at high frequency. Simulation results show that the circuit can achieve a 95% efficiency when the output voltage is controlled to be 2V with the load of lW.