A 0.0251 mm2Temperature Sensor Achieving a ±0.25 °C (3σ) Inaccuracy From –40 °C to 125 °C Without Backend Nonlinearity Correction

This paper presents a compact, high-accuracy and scalable on-chip temperature sensor (TS) optimized for low-power embedded applications, such as system-on-chip (SoC) and microprocessor thermal monitoring. The proposed TS employs a capacitive-biased-diode (CBD) structure enhanced by an adaptive discharging period (ADP) technique to achieve high sensitivity and linearity without additional backend calibration. The CBD sensor output is digitized by an oversampling (OS) successive approximation register (SAR) ADC with custom vertical metal-oxide-metal (VMOM) capacitors and a mismatch error shaping (MES) technique, providing high accuracy in a minimized chip area. Additionally, a discharging clock chopping (DCC) technique is proposed to effectively suppresses low-frequency noise with minimal switch noise, while clock boosters are implemented to decrease the ON-resistance of switches, reducing nonlinearity effects. Fabricated in a standard CMOS 180nm process, the sensor occupies only 0.0251 mm2 and consumes 3.6 µW. It achieves a one-point trimmed inaccuracy of ±0.25°C over a temperature range of −40°C to 125°C.