Experimental Measurements of an Integrated Hysteretic Controlled Regulating Buck Converter with Capacitively Coupled Bootstrapping

This paper presents the complete measured performance and characterization of an on-chip regulating buck converter with hysteretic control. The circuit was fabricated using the XFAB CMOS $0.35\ \mu \mathrm{m}$ high voltage technology and all the control circuit blocks were designed using analog techniques, with the transistors operating in the sub-threshold region, in order to minimize power consumption. All the high voltage transistors of the buck converter were implemented using 45V NMOS thin gate oxide layer transistors and are operated by means of a capacitively coupled bootstrap. The control circuit of the hysteretic regulator consumes between $194\ \mu\mathrm{W}$ and $420\ \mu \mathrm{W}$, and the proposed buck converter operates at a peak efficiency of 84.2%. The input voltage range of the regulator is from 1.5V to 45V and has a power range from $100\ \mu \mathrm{W}$ to 500 mW. The output regulated voltage is tunable via a feedback resistor and can be varied from 0.6V to 40 V, with a dropout voltage of 2 V.