A programmable integrated digital controller for switching converters with dual-band switching and complex pole-zero compensation

The design of a 0.6-mu m CMOS programmable integrated digital PID controller for a buck converter is presented. Several novel features are implemented. These include: 1) a dual-band switching scheme for sampling the output voltage for better output resolution; 2) a dual-band switching PWM generator with a modified tapped delay line for area efficiency; 3) a VCO driving a counter to serve as an ADC; 4) a programmable PID compensator employing variable integration times for enhancing accuracy and stability; and 5) complex pole-zero cancellation ill extending the bandwidth of the control loop. The converter is designed for variable output applications, and the fast digital loop achieves a tracking time of 50 mu s for a 1-V step change of the reference voltage. The converter switches at 1 MHz and attains a maximum efficiency of 90% when delivering a load of 125 mW.