A multi-mode digital controller with windowed ADC and self-calibrated DPWM for slew-enhanced switching converter

Windowed ADC is an attractive solution for the high efficiency digitally-controlled converters. However its limited conversion range restricts the transient speed for the dynamic voltage scaling applications. For slew rate improvement, this work designed a multi-mode PI/PID controller incorporated with the windowed ADC operation. In addition, to make output stable with no limit cycling, a current-controlled delay-line ADC and a DPWM with self calibration loops are proposed. The prototype chip is realized in a standard 0.18-μm CMOS process. The switching frequency of the buck converter is up to 5MHz. The average current consumed in the digital controller, ADC and DPWM are 0.25, 0.2 and 0.7mA, respectively. The transient time from 1-V to 1.7-V step is 30μs that is 2.5 times faster than the conventional linear controller design.