A High-accuracy And Low-power CMOS Temperature Sensor

In this thesis, the temperature characteristic of parasitical PNP transistor isanalyzed, and the calibration of high-accuracy temperature sensor is discussed. Besides,the way to reduce the effects of non-idealities of VBEand VBEis introduced. Based onthe analysis of temperature and process characteristic of VBEand VBE, a high-accuracyCMOS temperature sensor is proposed and realized. The proposed temperature sensor iscomposed of the PNP-based temperature sensing circuit, a low-speed high-resolutionADC and a high-accuracy calibration circuit. The temperature sensing circuit is basedon the temperature characteristic of VBEand VBE. Additionally, a variety of precisiontechniques, such as the chopping technique, DEM (dynamic element matching), thecompensation of second order non-linearity and the precision PTAT bias circuit, areadopted to overcome the impact of non-idealities. The low-speed high-resolution Σ-ΔADC is composed of the Σ-Δ modulator and the decimation filter. A first-order Σ-Δmodulator is used in the ADC for the compromise of dissipation and resolution. Thecalibration circuit is designed based on the conclusion that processing spread mainlyresults in a PTAT error in VBE. And the calibration circuit can easily be realized byadding a resistor in series with the emitter of the transistor which is biased at a PTATcurrent.Based on the SMIC0.18μm1P6M CMOS process model library, the proposedCMOS temperature sensor has been simulated by Cadence Spectre simulator. Thesimulation result shows that, by calibrating the sensor at room temperature, its accuracycan reach±0.42℃in the temperature range of-40℃～125℃. Besides, the proposedCMOS temperature sensor dissipates0.69mW power from a3.3V supply when itsconversion speed is60SPS.