A Temperature Sensor with 3 sigma Inaccuracy of+0.5/-0.75 degrees C and Energy per Conversion of 0.65 mu J Using a 0.18 mu m CMOS Technology

We present an integrated temperature sensor, which utilises bipolar transistors present in a 0.18 mu m CMOS process. A bipolar transistor is biased with two different current densities consecutively to have a voltage proportional to absolute temperature (PTAT). Two such bipolars are used to achieve a differential signal. The differential PTAT signal is fed to an incremental Delta Sigma. ADC to have temperature information in digital domain, which is then processed with an on-chip DSP block. The whole sensor can he put into power down mode after a conversion is done. The sensor operates in the temperature range from -40 degrees C to +85 degrees C. The energy per conversion is 0.65 mu J when the sensor output rate is at 3 conversions/s. The inaccuracy of the sensor is +0.51-0.75 degrees C (3 sigma) after three point fitting.