This paper presents the design of a monolithic current-mode CMOS DC/DC converter with integrated power switches and an on-chip passive adaptive controller with the sensed average inductor current. The sensed switched current, combined with the integration of inductor voltage, and a voltage-controlled floating resistor, can be used for the adaptive control of a CMOS DC/DC converter. The nonlinear carrier control can adjust carrier according to input voltage to reduce the input disturbance. The proposed control scheme has been design and simulation verified based on the TSMC 0.35μm technology. The designed CMOS DC/DC switching regulator is based on a rated output current of 500mA with an adjustable output voltage from 1.0V to 1.8V. Simulation results shows the proposed adaptive control scheme can achieve a fast dynamic power on transient response as well as a robust voltage regulation against large loading current variation.