A Low-Power BJT-Based CMOS Temperature Sensor Using a Common-Mode Error Suppression Sampling Scheme From −50 °C to 150 °C

A CMOS temperature sensor targeting automotive and industrial applications is presented. The sensor integrates a BJT-based sensing frontend with a second-order$\Sigma \Delta$ADC. To address the accumulation of common-mode error in the integrator under low supply voltages, which can lead to large input common-mode deviations that reduce the integrator amplifier gain and degrade the ADC SNR, a novel sampling scheme is proposed. By means of a carefully designed sampling sequence, the proposed scheme maintains the amplifier input common-mode voltage within a small and predictable range, thereby stabilizing the amplifier gain and preventing SNR degradation. In addition, the sampling scheme reduces the number of ADC input branches, which effectively minimizes leakage current. To further enhance the measurement accuracy, a finite BJT current-gain compensation resistor and a bitstream-controlled dynamic element matching (BSC-DEM) technique are employed in the sensing frontend. Fabricated in a 180 nm CMOS process, the prototype achieves an inaccuracy of$\pm$1.0$^\circ \mathrm{C}$(3$\sigma$) from -50$^\circ \mathrm{C}$to 150$^\circ \mathrm{C}$. The sensor consumes 6.3$\mathrm{\mu }$A from a 1.8 V supply at room temperature, achieves a resolution of 0.018$^\circ \mathrm{C}$, and occupies an active area of 0.1 mm$^{2}$.