A Reconfigurable Transient Optimizer Applied to a Four-Phase Buck Converter for Optimizing Both DVS and Load Transient Responses

Abstract

This brief presents a reconfigurable transient optimizer (RTO) applied to a four-phase buck converter for optimizing both dynamic-voltage-scaling (DVS) and load transient responses to approach the theoretically minimum output-voltage undershoot ${ \Delta }\text{V}_{\mathrm{US}}$ , overshoot ${ \Delta }\text{V}_{\mathrm{OS}}$ , and settling time $\text{t}_{\mathrm{S}}$ . The DVS and load transients are instantly detected by a voltage sensor and calibrated capacitor-current sensor, respectively. When a large DVS or load transient occurs, the RTO enables all four phases, reconfigures its circuit architecture, and controls the optimal ON–OFF times of the power switches, thereby settling the output voltage in a single ON–OFF switching with ${ \Delta }\text{V}_{\mathrm{US}}$ , ${ \Delta }\text{V}_{\mathrm{OS}}$ , and $\text{t}_{\mathrm{S}}$ close to their respective theoretical minima. The converter is fabricated in a 0.18- $ {\mu }\text{m}$ CMOS process with a 2.3-mm2 chip area. For a 1-to-1.8 V (1.8-to-1 V) DVS transient, the measured ${ \Delta }\text{V}_{\mathrm{OS}}$ ( ${ \Delta }\text{V}_{\mathrm{US}}$ ) is not observable, while the measured $\text{t}_{\mathrm{S}}$ is 182 ns (192 ns). For a 1.8-A step-up (step-down) load transient, the measured ${ \Delta }\text{V}_{\mathrm{US}}$ ( ${ \Delta }\text{V}_{\mathrm{OS}}$ ) and $\text{t}_{\mathrm{S}}$ are 56 mV (45 mV) and 85 ns (76 ns), respectively. Compared with other state-of-the-arts, this brief’s $\text{t}_{\mathrm{S}}$ in the DVS transient response is the closest to its theoretical minimum, while the ratios of ${ \Delta }\text{V}_{\mathrm{US}}$ , ${ \Delta }\text{V}_{\mathrm{OS}}$ , and $\text{t}_{\mathrm{S}}$ to their respective theoretical minima in the load transient response are comparable.