Research And Design Of High Precision Reference

The developing history, present situation and trends of temperature sensor and CMOS integrated temperature sensor were summarized in this paper. The dominance and properties of the CMOS integrated reference were also described,and the research meaning was pointed out.Related device theory and process model used in design were described. The temperature related model and the influencing factor of two active devices, subthreshold MOSFET and PNP substrate transistor, based on CMOS process were analyzed and compared, and pointed out that the PNP substrate transistor was more fit for being the temperature compensating device for bandgap reference. Related theory of important CMOS sub-circuits were also describled. According to the comparison of the types of the CMOS integrated reference,bandgap reference was choosed as the most mature in theory and most steady in performance.Through analysis of temperature compensation methods in lots of literature,it was pointed that only multi-order compensation method of temperature could minish temperature coefficient sharply. Piece-wise linear compensation method was fairly simple multi-order compensation methods of temperature, furthermore it was compatible with CMOS standard process through optimization. According to the theory of the bandgap reference,a PTAT current generator was designed, then the proportional voltage value to temperature could be achieved. The traditional bandgap reference circuit was improved in the design, which includes the applying of self-bias structure and cascode structure,output of the opamp was used as self-bias voltage,saving bias circuit,and then it was helpful to get low power consumption.Through using poly resistance of high value with low temperature coefficient,we reduced the influnce to circuit ,if power supply did not change,we must decrease operating current to decrease power consumption,and increasing value of resistor could decrease the operating current efficiently.Poly resistance of high value had large value of squared resistor,so we could save layout area. We obtained PTAT and CTAT current generator with low power consumption and high PSRR, which in a simple circuit structure. According to the comparison of related reference,the circuit had lower power consumption in the same process.More pieces meaned more complicated,so through the PTAT and CTAT current achieved above,we could accomplishd the simplest multi-order compensation of temperature,and got the output voltage with low tempereature coefficient.It was reasonable to use the PTAT and CTAT current achieved above to get reference current with low temperature coefficient through reasonable design.We simulated the reference circuit with simulation tool of Cadence Spectre:the temperature coefficient of bandgap reference voltage was 1.88ppm/°C,and its power supply rejection ratio was about -63.5dB,and the change of voltage was 0.195mV/V only with power supply,its power consumption was 144.2μW;As to current reference, its temperature was 113 ppm/°C, and its power supply rejection ratio was about -89.5dB,and the change of current was...