The Design Of On-chip Temperature Sensor Based On Bandgap Voltage

The design is based on HHNEC0.35um CMOS technology. This is ahigh precision on-chip temperature sensor, and the accuracy is±0.5℃.According to the design principle of band-gap, the chip produces a voltageΔVBE, which is proportional to absolute temperature. And then, the signalis amplified to a range that can be detected. Then, it is converted bysigma-delta ADC. After being modulated, the signal is passed to a digitalfilter. Then, the out-of-band noise is filtered by the low pass filter. withproper error compensation, the reading is output from I2C interface,realizing the on chip temperature detection.The thesis mainly describes the whole system design circuit in threeparts: band-gap PTAT current generator, current trimming, and ΔVBEgenerator. The design uses a traditional band-gap circuit in the front-end toproduce a PTAT current. In the circuit, we use chopper technology toreduce input offset in the operate amplifier. This method can eliminateerror in PTAT current caused by offset. For other accumulated errors in thefront-end, the system uses a current trimming circuit to calibrate it withsmaller area and higher accuracy. The design uses Dynamic ElementMatching (DEM) technology to decrease process mismatch, device errorand system error in circuit. And this technique is used to produce animportant parameter:ΔVBE. There are some flicker noise and input offsetin sigma-delta ADC design. But the design used chopper technology tomitigate these problems. Through these techniques, we designed a suitablemodulate for T-sensor. At last, an important topic describes how to test andcalibrate the packaged chip. We find some method to solve many problemsrelated to testing, such as oil groove correction, golden chip and single point to test curve etc. Through these methods, we successfully achievedthe design SPECs, and realized mass-production of the chip.