A Sub-1-V, High PSRR, Subthreshold MOSFET-only Voltage Reference for Wireless Sensor Networks

With the recent advancements in ultra-low power wireless devices such as wireless sensor networks, the demand for nanowatt voltage references capable of operating below 1-V becomes a necessity. But due to the low voltage overhead imposed by the supply, most of the recent literatures on sub-1-V voltage references exhibited low power supply rejection ratio (PSRR) and thus were prone to switching noise induced at the supply line. This paper presents a high PSRR, subthreshold MOSFET-only voltage reference which has been simulated in 0.18 μm TSMC CMOS process using the Synopsys HSPICE tool. The circuit employed a PSRR enhancement block that suppresses the variation along the supply of the core voltage reference. This circuit block implemented a negative feedback network that regulated the internal supply voltage of the core reference circuit. Simulation results showed that the proposed overall circuit generated an output voltage of 244.5 mV which operated properly at a supply voltage of 0.95-V and achieved a PSRR of -140.6 dB, -101.1 dB, - 64.3 dB, and -38.4 dB at 100 Hz, 1 kHz, 10 kHz, and 10 MHz respectively. The circuit also achieved a temperature coefficient of 9.9 ppm/
^o
C from -25 °C to 100 °C while consuming only 74.6 nW. From these results, the designed high PSRR voltage reference provides the necessary specifications suitable for wireless sensor network nodes.