An Accuracy-Improved and Internal Regulator-Free Temperature Sensor With a Non-Linear Current Mode Feedback Pseudo-PLL

An accuracy-improved and internal regulator-free temperature on-chip sensor is proposed. The proposed sensor outputs an accuracy-enhanced pulse width modulation (PWM) signal with a nonlinear current mode feedback pseudo-PLL (Phase-Locked Loop). The pseudo-PLL is able to greatly mitigate the nonlinearity caused by process parameters (eg. threshold voltage and mobility of MOS transistor) without careful compensation. Furthermore, to optimize the area and power supply rejection without an internal regulator, a current mode input and feedback approach in the pseudo-PLL is also presented. The proposed sensor is fabricated with 0.18~\mu \text{m} standard CMOS process. The measurement results show that the power consumption of the sensor is only 2~\mu \text{W} under 1.2V supply voltage. With the supply voltage varying within 1~1.2V, the temperature detection error is maintained within +/−0.2°C in the range of −20°C to 100°C. And the corresponding power supply rejection (PSR) ratio and resolution achieve about 0.15°C/100mV and 0.12°C, respectively.