An On-Chip CMOS Temperature Sensor Using Self-Discharging P-N Diode in a $\Delta$ - $\Sigma$ Loop

A CMOS temperature sensor to monitor on-chip distributed thermal profile of high-performance system-on-chips (SoCs) is presented. The architecture of this sensor utilizes a self-discharging p-n diode to implement a first-order delta-sigma ( $\Delta$ - $\Sigma$ ) loop. To determine the on-chip temperature, the temperature-dependent reverse-bias leakage current of the diode is measured. The sensor is implemented in a 0.18- $\mu \text{m}$ CMOS process and it occupies a small area of $550\mu \text{m}^{2}$ . Performance measurements demonstrate the on-chip sensor inaccuracies of ±0.1 °C ( $3\sigma$ ) with calibration, and ±0.5 °C ( $3\sigma$ ) without any calibration, over 35 °C–100 °C, which is the functional temperature range of current high-performance SoCs. The sensor, excluding the digital and any reference generators, consumes $4\mu \text{W}$ from a single 1.8-V supply. The worst case resolution of the sensor is 75 mK at 2-Hz bandwidth with the overall sensor figure of merit of 11 nJ°K 2 .