A 6 A, 93% Peak Efficiency, 4-Phase Digitally Synchronized Hysteretic Buck Converter With ±1.5% Frequency and ±3.6% Current-Sharing Error

Abstract

A four-phase, quasi-current-mode hysteretic buck converter with digital frequency synchronization, online comparator offset-calibration and, digital current-sharing control is presented. The switching frequency of the hysteretic converter is digitally synchronized to the input clock reference with less than ±1.5% error in the switching frequency range of 3–9.5 MHz. The online offset calibration cancels the input-referred offset of the hysteretic comparator and enables ±1.1% voltage regulation accuracy. Maximum current-sharing error of ±3.6% is achieved by a duty-cycle-calibrated delay line-based pulsewidth modulation generator, without affecting the phase synchronization timing sequence. In light-load conditions, individual converter phases can be disabled, and the final stage power converter output stage is segmented for high efficiency. The dc–dc converter achieves 93% peak efficiency for $V_{i}= 2$ V and $V_{o}= 1.6$ V.