An 11.2nW, 0.45V PVT-tolerant Pulse-width Modulated Temperature Sensor in 65 nm CMOS

Abstract

This paper presents a low power temperature sensor in 65 nm CMOS. The architecture is digital friendly because it creates a pulse-width modulated (PWM) output instead of a DC voltage; hence, it can be directly interfaced with a digital counter instead of a power-hungry analog-to-digital converter. The proposed design does not use a reference current, which is the prime energy consumer in most temperature sensors, due to required feedback amplifiers. Additionally, reference current devices require large voltage headroom while their resistors occupy large die area. The proposed design expresses the output as a ratio, relative to a reference pulse. Therefore, it is less susceptible to process-voltage-temperature (PVT) variation. The proposed design achieves a temperature accuracy of +0.23°C to-0.22°C within the temperature range-20-80°C, while consuming only 11.2nW at 27°C, while operating from a supply voltage as low as 450 mV.