An Energy‐Efficient Fully On‐Chip CMOS Temperature Sensor for Portable Applications With an RFoM of 2.79 pJ.K²

ABSTRACT This article describes an energy‐efficient, low‐power CMOS temperature sensor suitable for portable applications. The sensor's front‐end circuitry is designed with a reference voltage (V ), complementary to absolute temperature (CTAT) voltage (V ), and ramp voltage generators. The ramp voltage (V ) is produced by utilizing a current reference circuit. The ramp voltage is compared with independent and temperature‐dependent voltages to perform the voltage‐to‐frequency conversion. Conversion from frequency to digital output is achieved through an asynchronous counter with an on‐chip oscillator. The proposed design is realized in a 0.18‐ m CMOS technology and attains a power usage of 604.4 nW at 27°C with an operating voltage of 0.5 V. Furthermore, it obtains an inaccuracy of +0.71/−0.73°C over −40°C to 125°C temperature range with an active area of 0.025 mm 2 . Moreover, the designed sensor circuit offers a resolution of 0.17°C with an energy conversion of 96.7 pJ.