A CMOS smart temperature sensor with digital output is presented. It c
onsumes only 7 mu W. TO achieve this extremely low-power consumption,
the system is equipped with a facility that switches off the supply po
wer after each sample. The circuit uses substrate bipolars as a temper
ature sensor. Conversion to the digital domain is done by a sigma-delt
a converter which makes the circuit highly insensitive to digital inte
rference, The complete system is realized in a standard CMOS process a
nd measures only 1.5 mm(2), In the temperature range from -40 to +120
degrees C, the inaccuracy is +/-1 degrees C after calibration at two t
emperatures, The circuit operates at supply voltages down to 2.2 V.