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 ΔΣ 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 mm² and consumes 2.9 μW from a 0.8-V supply. It achieves a 1-point trimmed inaccuracy of ± 0.4 °C (3σ) from -40 °C to 125 °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

This article presents a 14-bit fully dynamic sensor interface that consists of a switched-capacitor (SC) ΔΣ modulator and a dynamic bandgap reference (BGR). The BGR is implemented by summing the proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) outputs of two PNP-based capacitive DACs. At the sampling rate, the DAC capacitors are pre-charged to the supply and then discharged for a fixed period via PNPs, thus biasing them and simultaneously sampling their base-emitter voltages. By using the modulator's first integrator to sum the DAC outputs, a dynamic BGR can be realized, which does not need additional reference buffers or decoupling capacitors. To make the system fully dynamic, the modulator itself is based on capacitively biased (CB) floating inverter amplifiers (FIAs). Implemented in a standard 130-nm CMOS process, the sensor interface occupies an area of 0.2 mm². It achieves an SNDR of > 84.5 dB over a scalable bandwidth (BW) ranging from 98 Hz to 5.9 kHz while consuming 1.7-50.8 μW. Furthermore, by employing a time-domain temperature-compensation scheme, it achieves a batch-trimmed gain error of ± 0.26% from -40°C to 125 °C.