High accuracy remote temperature sensor based on BJT devices in 0.13-μm CMOS

This paper presents the design of a BJT-based remote temperature sensor to measure ambient temperature in different locations. The sensor chip supplies a calibrated current to the external devices, which are common off-the-shelf bipolar junction transistors - 2N3904 (NPN) and 2N3906 (PNP), and converts their base-emitter voltages to temperature using a 13-bit charge-balancing ΣΔ modulator. Dynamic element matching, correlated double sampling and system-level chopping techniques are deployed to reduce temperature errors due to non-ideal effects of CMOS readout circuitry. A prototype sensor has been fabricated using 0.13-μm CMOS process. Measurement results show that the temperature sensor inaccuracy is ±2 °C from -40 °C to 125 °C.