A 2.1 ppm/°C, 0.55–2.4 V, 5.6 nW, 235 mV, CMOS-only subthreshold voltage reference

Abstract

This study presents a high-precision, ultra-low-power, and CMOS-only subthreshold voltage reference. VPTAT with a positive temperature coefficient (TC) and VCTAT with a negative TC were generated to obtain a low-temperature dependence voltage reference. VPTAT was implemented using two standard-threshold voltage (STV) transistors working in the subthreshold region, while, VCTAT was implemented by a high-threshold-voltage (HTV) transistor and an STV transistor biased in the subthreshold region to obtain a ΔVGS with a negative TC. The voltage reference circuit was implemented via a standard 0.18-μm CMOS process with the core size around 0.022 mm2. The pre and post simulation results showed an average output reference voltage of around 235 mV with different supply voltages. Under a temperature range of −30 to 80 °C and the supply voltage of 0.55 V, the best TCs were as low as 2.1 and 7.6 ppm/°C for pre and post simulations, respectively. The total power consumption was only 5.6 nW when the supply voltage is 0.55 V.