Right now, I am considering to desing an IC which could sense the temperature. I only have access to common process like TSMC 0.18, thus I can only use techniques within the chip. Can you give me some suggestion?
by using temperature dependent element like voltage of diode or PTAT current.
As a starting point I would suggest to check the bandgap voltage reference, I would simply modify a basic bandgap....
It depends on how accurately you would like to sense the temperature and also what temperature range you are interested in. The other posters in this thread have suggested some good ideas (I myself use a PTAT temperature sensor).
If it is silicon based you can use the vertical or lateral parasitic bipolar to generate a PTAT signal and the reference is from the bandgap reference signal. In addition you might want to interface a first order sigma delta converter for digital readout. Depending on your accuracy requirements you might need additional front end circuitry and higher order modulators for the Delta Sigma ADC