A hysteretic buck converter employs a hybrid voltage/current mode control to regulate output voltage and switching frequency independently. Fabricated in a 130nm CMOS process, the prototype consumes only 50μA quiescent current and operates at a constant switching frequency of 1MHz over a wide range of output voltages (0.7-to-1.8V) and inductor values (1-to-5μH) with a peak efficiency of 93%. The output ripple and the settling time of the converter are less than ±2.5mV and 10μs, respectively. © 2012 IEEE.