This paper presents a four-phase buck converter with capacitor-current-sensor (CCS) calibration for load-transient-response optimization that targets the theoretically minimal output-voltage undershoot ΔVUS, overshoot ΔVOS, and settling time tS when large and rapid load-current transients ΔIload occur. The proposed CCS calibration calibrates the CCS' equivalent impedance to emulate a scaled replica of the output capacitor's impedance ZCo. Thus, the CCS can accurately sense the output-capacitor current ICo despite ZCo variations due to different output voltages, fabrication variations, and printed-circuit-board parasitics. Moreover, a load-transient optimizer is proposed to utilize the accurately sensed ICo to instantly detect the large and rapid ΔIload, and synchronously control the charging and discharging durations of the output inductors in all four phases, resulting in small ΔVUS/ΔVOS and short tS. The converter is implemented in a 0.18-μm CMOS process with 1.93-mm2 chip area. For a 1.8-A/5-ns step-up (step-down) ΔIload, the measured ΔVUS (ΔVOS) and tS are 92 mV (75 mV) and 133 ns (110 ns), respectively. Compared with other state-of-the-arts, both the measured ΔVUS (ΔVOS) and tS in this paper are the closest to their respective theoretical limits, i.e., the fastest load-transient response with the smallest ΔVUS (ΔVOS) and the shortest tS under the same input voltage, output voltage, output inductance, and output capacitance.
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering