Low-power CMOS Temperature Sensor Based On Subthreshold Current Ratio

With the rapid development of science and technology and the continuous improvement of the level of social development,the continuous research and breakthroughs in the performance of semiconductor devices have made the integration of circuits on the same area more and more high,resulting in the continuous increase of the temperature non-uniformity of the entire circuit.Therefore,temperature sensors are increasingly important for temperature management of modern high-performance microprocessors and system-on-chip.Usually,dozens of temperature sensors are installed on the same chip for real-time cold spot and hot spot detection.The temperature sensor has different performance requirements under different application conditions.For example,in the field of industrial control,the sensor should have a wide range of indicators,but the demand for temperature sensing accuracy is relatively broad;In the field of intelligent wearable consumer electronics,sensors should have the characteristics of low power consumption and small size;For on-chip temperature management,sensors need to have low power consumption,small size,wide range,and good power supply rejection.CMOS temperature sensor,which has the outstanding advantages of small size,low power consumption,low cost and easy integration for on-chip thermal management applications,has received extensive attention from academic researchers.In this thesis,the temperature characteristics of CMOS process are carefully studied and a temperature sensor is designed based on the performance requirements of temperature sensors in the above application fields.The temperature sensor is composed of voltage compensation module,temperature sensing module,current-frequency conversion module and counter module.It has low power consumption,small size,wide range,and good power supply rejection capability.The voltage compensation module uses the CTAT voltage generated by the gate tunneling current to compensate the voltage of the temperature sensing module;In the temperature sensing module,the sub-threshold current ratio is used for temperature sensing to meet the requirements of low power consumption and small size;The current-frequency conversion module uses a current comparator to reduce the area and power consumption of the circuit;The counter module uses programmable counters to convert the frequency ratio into digital signal output and realize adjustable resolution.In addition,based on the careful analysis and full use of the Shallow trench isolation effect and the substrate bias effect,the shortcomings of the sensor’s temperature sensing accuracy seriously deteriorated with the process angle are overcome.Based on 40nm CMOS technology,the temperature sensor proposed in this thesis is designed and verified.The power consumption of the whole circuit is 73n W,which meets the application requirements of low power consumption.In the temperature sensing range of-40℃-125℃,all process corners can meet the temperature sensing accuracy of-1℃/0.7℃,and the circuit area is only 0.004mm~2,which is suitable for the application of multiple integration fields.In the 1.4V-1.8V supply voltage range,the temperature sensing accuracy of the temperature sensor is better than 1.3℃,and the power supply sensitivity is less than 1.5℃/V.