Design Of Digital CMOS Temperature Detecting Circuit

Temperature is a basic physical quantity,and one of the key physical parameters necessary for industrial and agricultural production and scientific research.With the advent of the information age and the public's attention to public safety,health monitoring,environmental protection and many other fields,the importance of temperature sensors is constantly improving.Integrated temperature sensor combined with the temperature sensor and integrated circuit technology,has the advantages of low cost,low power consumption,high precision and various functions etc.,so it owns more broad application platform,especially in networking applications,the integrated temperature sensor is essentialBased on the analysis of the development of temperature sensors at home and abroad,a new type of temperature sensor is designed.Unlike traditional ADC-based temperature sensors,this temperature sensor uses TDC to quantify the signal First of all,the design of two kinds of temperature sensing circuit:temperature current pulse conversion circuit based on temperature sensing current,generates proportional to absolute temperature(PTAT)delay and complementary to absolute temperature(CTAT)delay by resistance and resistance using integrated active MOS.Time delay difference,as the output delay improve the linear relationship between and temperature;temperature current pulse conversion circuit,based on temperature sensing voltage,controls the charging time of capacitor by PTAT delay and CTAT delay produced by subthreshold MOS PTAT voltage and CTAT voltage,Time delay difference,as the output delay,improve the linear relation between the output time and temperature.In order to improve the temperature stability of TDC,this paper selects PLL-TDC.Phase Locked Loop(PLL)produces an accurate clock signal and clock phase uniform,which is used as the TDC clock signal measurement,a multistage TDC step quantization,both range and resolution,and to improve the system stability.Fabricated in GSMC 0.18?m CMOS technology,the Cadence EDA tools,such as Virtuo,is adopted to complete the entire circuit's pre-simulation,layout design,post-simulation.The results of post-simulation show that:in the temperature range of-20?-120?,1.8V power supply voltage,a temperature sensing circuit based on temperature sensing current can achieve accuracy of 1.290C,the resolution is less than 0.1?,which meet the design requirements.In the temperature range of-20 ??120 ? temperature sensing circuit based on temperature sensing voltage,can be achieved within accuracy of 1.31 ?,the accuracy has meet the design requirements.And PLL-TDC achieves 500ps resolution at the 15.625MHz input reference clock conditions.