A 80kS/s 36µW resistor-based temperature sensor using BGR-free SAR ADC with a unevenly-weighted resistor string in 0.18µm CMOS

A resistor-based temperature sensor with a BGR-free SAR ADC is reported. The non-zero temperature dependency of the ADC reference voltages, as a result of without using a BGR, is compensated by adopting the proposed unevenly-weighted 9-bit resistor string for reference voltage generation. Fabricated in a 0.18 μm CMOS, the sensor achieves 0.25°C resolution over 0~100°C range and draws 20 μA from a 1.8 V supply. At a conversion rate of 80 kS/s, the FOM is 0.11 nJ/°C.