Low cost CMOS on-chip and remote temperature sensors

Abstract

This paper describes the design and results of low cost integrated CMOS local and remote temperature sensors with digital outputs. No trimming is needed to obtain good temperature linearity, so that only one-temperature calibration is needed which greatly reduces testing cost. The base-emitter voltage of the parasitic substrate bipolar transistor is used to measure the local temperature. A diode-connected external bipolar transistor is used to measure the remote temperature. Chopper techniques were used to cancel the offset voltage of the op-amp, so that a precise bandgap voltage call be obtained without resistance trimming. A first order Sigma Delta ADC was used to produce the digital output. The local and remote temperature sensors were realized in a 0.6 mu cm single-poly triple-metal CMOS technology with active area of 0.61 nm(2) and 0.65 mm(2), respectively. After calibration, the error is +/-1 degreesC for the local temperature sensor over the temperature range of -20 to 130 degreesC, and +/-2 degreesC for tile remote temperature sensor over the range of 0 to 120 degreesC. The supply currents of tile local and remote temperature sensors are 3.5 muA and 38 muA at 8 samples/s, respectively.