Nowadays the integrated circuit is usually in need of various voltage supports. To efficiently manage the power demand, numbers of power modules are integrated together to form a power management unit (PMU). Since each power module has its own spec, the controller inside the power module is usually independent. The independent controller with its own signal process scheme definitely occupies certain circuit area, which is not area efficient as the number of power module increases inside the PMU. Therefore, a controller sharing concept is proposed for saving the circuit area. The controller sharing solution is stemmed from the time multiplexing concept. Based on the discrete feature of the digital control, several hardware segments of the controller can be shared for different power modules without affecting individual performance. Detail of the controller sharing model in time domain is built on MATLAB Simulink software to verify the feasibility of the controller sharing mechanism.