A Sub-1-V Capacitively-Biased Voltage Reference With an Auto-Zeroed Buffer and a TC of 18-ppm/°C

Abstract

This brief presents a capacitively-biased CMOS voltage reference, which can operate from a sub-1V supply while achieving a low temperature coefficient (TC) and a competitive power-supply rejection ratio (PSRR). The reference voltage is generated by a capacitive bias circuit that provides a well-defined proportional-to-absolute-temperature (PTAT) bias current for a $\Delta $ Vth type reference that consists of two stacked MOSFETs with different threshold voltages. The generated output voltage is sampled by an auto-zeroed (AZ) buffer, which can drive capacitive loads up to 2 nF. Fabricated in a 65 nm CMOS process, the prototype voltage reference occupies 0.058 mm2, including the AZ buffer and an on-chip timing generator. It outputs a reference voltage of 204.1 mV with a minimum supply voltage of 0.7 V. It achieves a TC of 18 ppm/°C from $- 40~^{\circ }$ C to $85~^{\circ }$ C and a PSRR of −75 dB at 100 Hz with only $200~\mu $ V ripple.