All–MOS self-powered subthreshold voltage reference with enhanced line regulation

Abstract A self-powered nano-watt voltage reference circuit has been developed for the integrated microsystems realized in standard CMOS technology. The circuit is highly immune to the temperature variations, and its output voltage can be made very insensitive to the power supply glitches in connection with a simple regulation mechanism used to harvest energy from the environment. The proposed reference is an all-MOS topology without any operational amplifier or on-chip resistors, generating a stable output with excellent line regulation owing to the modifications applied to suppress the power supply variations. All the MOS devices are working in weak inversion to ensure operation at nano-ampere current levels. Simulated in 0.18-µm standard CMOS process, a prototype of the proposed reference consumes an overall power of 14 nW at 0.7 V minimum supply. The average voltage reference is 255 mV with an average temperature coefficient of 17.05 ppm/oC across –40°C to +125°C. The line regulation is 0.00797 %/V and 0.00456 %/V, respectively, when the circuit is subjected to input supply variations of 0.9 V – 2.0 V and 1.0 V – 2.0 V. The power supply rejection ratio is –110 dB, –91 dB and –68 dB for 0.1 Hz, 10 Hz, and 1 MHz at room temperature, respectively.