A 0.8-V BJT-Based Temperature Sensor With an Inaccuracy of $\pm$ 0.4 $^\circ$ C (3 $\sigma$ ) From $-$ 40 $^\circ$ C to 125 $^\circ$ C in 22-nm CMOS

This article presents a compact sub-1-V bipolar junction transistor (BJT)-based temperature sensor for thermal management applications. To operate from a sub-1-V supply, two capacitors are first pre-charged to a supply-independent initial voltage ( $>$ 1 V) by regulated charge pumps (RCPs) and then discharged through two diode-connected BJTs. By using different discharge times, proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) voltages can be generated. These are then read out by an area-and energy-efficient charge-balancing $\Delta\Sigma$ modulator to generate a digital representation of temperature. To reduce its noise, the modulator’s first inverter-based integrator employs both chopping and auto-zeroing. Fabricated in a standard 22-nm bulk CMOS process, the sensor occupies 0.01 mm $^2$ and consumes 2.9 $\mu$ W from a 0.8-V supply. It achieves a 1-point trimmed inaccuracy of $\pm$ 0.4 $^\circ$ C (3 $\sigma$ ) from $-$ 40 $^\circ$ C to 125 $^\circ$ C, which is the best reported in sub-65-nm CMOS. It also achieves high energy efficiency, resulting in a resolution figure of merit (FoM) of 0.41 $\text{pJ} \cdot \text{K}^2$ .