An output-capacitor-free buck converter with nano-second-DVS and sub-switching-cycle load transient response

An output-capacitor-free switching buck converter is proposed in this paper. By removing the off-chip capacitor, both the PCB footprint and system volume can be reduced. Due to the smaller output capacitance and added pull-up/down power transistors, the dynamic voltage scaling (DVS) tracking speed can be improved to nano-seconds/volt level. The load transient response of the proposed switching converter is also improved within one switching cycle. The proposed buck converter is designed with TSMC 0.35-μm CMOS process, regulating a 1.2~1.8V output voltage from a 3-V input power supply at 2-MHz switching frequency. A 63-ns/V DVS tracking speed is achieved with 100-pF filtering capacitor. The output voltage is recovered within one switching cycle when a 270mW load change occurs.