A New Sub-1 Volt 17 ppm/°C Offset-Insensitive Resistorless Switched-capacitor Bandgap Voltage Reference

摘要

A new PVT compensated voltage reference is presented by using switched-capacitor (S.C.) technique. In the proposed bandgap voltage reference (BGR), a p-n junction is biased with different currents during two different phases and required PTAT and CTAT voltages generated and held by two capacitors. Using a capacitive voltage divider, the PTAT voltage is weighted such that the sub-1V bandgap voltage is achievable. In order to cancel the effect of op-amp offset and to relax the design of op-amp, the offset voltage of the op-amp is sampled by a capacitor during a specified phase and inversely is added to the final bandgap voltage in next phase. The analysis of the proposed S.C. BGR is supplemented by simulation of a 0.5-V BGR with 28 mu W power consumption in a standard 0.18 mu m CMOS technology. Simulation results show that the average temperature coefficient of the S.C. BGR is 17 ppm/degrees C and it is robust against the process variations. Applying an arbitrary 100-mV op-amp offset results in a lower than 1.1 mV deviation in generated reference voltage. Due to the better matching of MIM capacitors in CMOS process (rather than resistors used in conventional BGR) the proposed S.C. bandgap provides good accuracy without any post trimming. Monte-Carlo analysis shows that sigma/mu of the generated reference voltage is as low as 0.7%. The sensitivity of the proposed BGR to supply variation is also less than 1%/V.