A fully integrated switch capacitor step down DC-DC converter in 65nm bulk CMOS technology with peak efficiency tracking

Abstract

This paper presents a DC-DC converter to be embedded in the pixel front-end of detectors in Large Hadron Collider (LHC) experiment at CERN. The DC-DC converter has to operate in a hostile environment due to the radiation. Under radiation, the value of the resistances, Ron, of the MOS switches changes. In addition, the load current, Iout, can change, ranging around the nominal value of 400mA from 200mA to 600mA. Both Ron and Iout, determine the optimum frequency that maximize the efficiency. In order to improve the efficiency as the operation conditions of the DC-DC converter changes, a tracking circuit of the peak efficiency was implemented. The tracking circuit performs a closed loop control of the clock frequency of the DC-DC converter. This converter provides an 800mV output voltage from a 1.2V input supply reaching an 80.22% peak efficiency. It is integrated in 65nm bulk CMOS technology with an area of 1.31mm2.