A Monolithic Capacitor-Current-Controlled Hysteretic Buck Converter With Transient-Optimized Feedback Circuit

This paper proposes a monolithic capacitor-current-controlled hysteretic buck converter with a transient-optimized feedback circuit (TOFC) for compact-sized portable devices. The proposed TOFC simultaneously optimizes both load and dynamic voltage scaling (DVS) transient responses to minimize output voltage undershoot/overshoot and settling time. In addition, a transient-hold (TH) technique, which prevents transient response optimization from being affected by the error amplifier without increasing the compensation capacitance, is also proposed to save chip area. This work is implemented in a 0.35 μm CMOS process with a chip area of 0.88 mm 2 . Measurement results show that, for a 500 mA load transient, the output voltage settles in 0.9 μs with an undershoot/overshoot of less than 35 mV. For a 0.6-V DVS transient, output voltage settles in 3 μs with negligible undershoot/overshoot. Moreover, 96% peak efficiency is measured at 500 mW output power.