Research And Design Of Low Power Temperature Sensing Circuit Based On CMOS Process

The integrated circuit is the foundation and core component of the information industry.It is a basic,leading and strategic industry related to the development of the national economy and society.Sensors are the only way for various chips to obtain external environmental information.Temperature sensors occupy more than 15% of the sensor market.Therefore,it is very necessary to study the temperature sensors.At first,the history,current situation and development trend of temperature sensors are summarized in this thesis.The characteristics and advantages of CMOS temperature sensing circuits are expounded.Then,the architectures of the existing temperature sensing circuits are analyzed,and our CMOS temperature sensing circuit architecture based on the time-to-digital conversion circuit is given.The circuit schematic diagram is designed and the pre-simulation is completed.Finally,the layout and post-simulation results of the temperature sensing circuit are given.The main works of this thesis are as follows:1.In order to reduce power consumption of the temperature sensing circuit,a picowatt-level ultra-low power reference voltage source is proposed in this thesis.To obtain a reference voltage with good temperature characteristics at different process corners,the gate-source voltage difference of different types of MOS transistors are used,which operated in the sub-threshold region.The power can be effectively reduced.2.Aiming at the clock signal problem of the temperature sensing circuit,a programmable frequency divider is proposed in this thesis.The frequency divider is designed based on a programmable down-counter.It is currently the rare programmable frequency divider that can achieve all modulus range and a 50%output duty cycle at the same time.By dividing the frequency of the input clock,it is obtained the clock signal which is required by the temperature sensing circuit.3.Aiming at the temperature measurement error of temperature sensing circuit,a current subtraction circuit is used in this thesis.By increasing the slop of the voltage difference between two voltages that vary with temperature,the resistance of this circuit to noise is increased.Thus,the temperature measurement error of the temperature sensing circuit is reduced.4?Aiming at the area problem of the temperature sensing circuit,an improved Time-to-Digital Converter is used in this thesis.Compared with the traditional Analog-to-Digital Converter,the design of our Time-to-Digital converter is simple.Compared with the traditional Time-to-Digital converter,a branch circuit of capacitor charging and discharging is reduced in our design.Thus,the area of the temperature sensing circuit is effectively reduced.0.18 ?m CMOS process is adopted by the low-power temperature sensing circuit and the design and simulation are completed.The simulation results show that the temperature sensing circuit has a temperature measurement error of 0.67/-0.52 ?within the range of-40 ? to 70 ?.Under a supply voltage of 1 V,the power consumption is 1.014 ?W,and a layout area is 0.091 mm~2.