A 0.5 V, 650 pW, 0.031%/V Line Regulation Subthreshold Voltage Reference

This paper presents a self-biased subthreshold voltage reference using the VTH difference between a thick-oxide MOS and a thin-oxide MOS to compensate the thermal voltage's temperature coefficient (TC). Based on theoretical analysis, the thick-oxide MOS's drain is selected as the output with optimized bias current, resulting in a robust voltage reference insensitive to process and supply variations. Fabricated in a 0.18-µm 1.8 V/ 3.3 V CMOS process, the proposed circuit achieves a line regulation of 0.031%/V under a supply voltage range from 0.5 to 2.2 V and a PSRR of −61.5 dB at 100 Hz before trimming. Under 25°C and a 1.2-V supply voltage, the average output voltage before trimming for 27 samples is 211.46 mV with standard deviation of only 0.64 mV (a/µ = 0.3 %). The average TCs before and after trimming are 152.8 and 11.4 ppm/°C, respectively, with total power consumption of 650 pW at 0.5 V and active area of 0.0012 mm2.