Low-ripple hysteretic-controlled monolithic buck converter with adapted switching frequency for large step-down ratio applications

20V maximum input voltage and 1A load current hysteretic control based monolithic buck converter with phase locked loop (PLL) is presented. To achieve advantage of hysteretic control and reduce inductor current ripple with ceramic output capacitor, hysteretic based control with PLL is adopted. Furthermore, in order to decrease inductor current ripple due to wide input voltage range, switching frequency is adapted to the input supply voltage. This buck converter is fabricated with 0.35 μm high voltage BiCMOS-DMOS (BCD) process.