A 1.2V Self-Referenced Temperature Sensor With a Time-Domain Readout and a Two-Step Improvement on Output Dynamic Range

A self-referenced temperature sensor with a time-domain readout and a two-step improvement on output dynamic range is presented in this paper. The proposed temperature sensor utilizes BJTs to generate temperature dependent/independent currents, which are converted to digital bits using a ring-oscillator-based time-domain readout scheme. A novel two-step improvement on output dynamic range is proposed to improve the power-efficiency and simplify the hardware design with a high conversion rate. Furthermore, the adopted process compensation strategy and the self-referenced readout scheme make the whole temperature sensor robust to process and supply variations. Fabricated in a standard 0.13- $\mu \text{m}$ CMOS process, the proposed temperature sensor occupies a die area of 0.06 mm 2 and consumes 9.92 nJ per conversion at a conversion rate of 75 kSa/s. After one-point calibration at 20 °C, the sensor achieves inaccuracies of −2.88 °C/+2.71 °C and −1.7 °C/1.36 °C from −20 °C to 100 °C, with and without systematic nonlinearity removal, respectively. It shows an average supply sensitivity of 0.0136 °C/mV from 1.05 V to 1.4 V without any external reference clock or voltage regulators.