Monolithic quasi-sliding-mode controller for SIDO buck converter in PCCM

An analog implementation of a novel fixed-frequency nonlinear controller for single-inductor dual-output (SIDO) buck converter in pseudo-continuous conduction mode (PCCM) is presented in this paper. Both the small and large signal variations around the operation point are considered to achieve better transient response so as to further reduce the cross regulation of this SIDO buck converter. Moreover, an internal integral loop is added to suppress the steady-state regulation error introduced by conventional PWM-based sliding mode controller. To verify the feasibility of this novel fixed-frequency quasi-sliding mode controller, a SIDO buck converter with two regulated output voltages (1.8V and 3.3V) is designed and fabricated in HEJIAN 0.35µm CMOS process. Simulation and experiment results show that when the first load changes from 50mA to 100mA, the transient time of this SIDO buck converter can be as low as 10µs while cross regulation is almost eliminated.