A 419pW Process-Invariant Temperature Sensor for Ultra-Low Power Microsystems

The paper presents a sub-nW BJT based temperature sensor for ultra-low power microsystems. The sensor is based on amplifying the difference between base-emitter voltages of BJTs using gate-leakage transistors. Implemented in UMC 65nm technology, the sensor occupies an area of 0.005mm ² . It achieves a maximum non-linearity error of 0.12 ^o C(3σ) over the temperature range of - 55 ^o C to 80 ^o C. Without any trimming, a worst case inaccuracy of +0.36 ^o C/ - 1.61 ^o C is observed w.r.t process variations, depicting the process-invariant nature of the temperature sensor. It also achieves a low supply sensitivity of 0.56 ^o C/V over a wide supply range of 0.7V-3V. The power consumption of the sensor is 419pW at 27 ^o C and 0.7V supply.