Transistor temperature measurement for calibration of integrated temperature sensors

A temperature measurement technique is presented for calibrating packaged integrated temperature sensors. An on-chip bipolar transistor is used to accurately determine the sensor´s temperature during calibration. The transistor´s base-emitter voltage is measured at three collector currents to find the absolute temperature while compensating for series resistances. The technique does not increase the pin count for a typical smart sensor, as the transistor can be accessed via the supply pins and an existing digital input pin. Measurements on substrate pnp´s in a standard CMOS process show that the temperature can be determined with an accuracy of ±0.1°C in the range of -50-130°C.