A temperature sensor with 3σ inaccuracy of +0.5/-0.75 °C and energy per conversion of 0.65 μJ using a 0.18 μm CMOS technology

We present an integrated temperature sensor, which utilises bipolar transistors present in a 0.18pm 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 ΔΣ ADC to have temperature information in digital domain, which is then processed with an on-chip DSP block. The whole sensor can be put into power down mode after a conversion is done. The sensor operates in the temperature range from −40 °C to +85 °C. The energy per conversion is 0.65 μJ when the sensor output rate is at 3 conversions/s. The inaccuracy of the sensor is +0.5/-0.75 °C (3σ) after three point fitting.