A Time Domain Mixed-Mode Temperature Sensor with Digital Set-Point Programming

To realize the on-chip temperature monitoring of VLSI chips, an accurate time domain mixed-mode CMOS temperature sensor based on delay lines is proposed. Without any bipolar transistor, a temperature sensor composed of single delay line is utilized to generate the delay time proportional to the measured temperature. A succeeding multiplexer (MUX), instead of conventional voltage/current DAC or external resistor, along with a reference delay line is used to program the set-point. The test chips were fabricated in a TSMC CMOS 0.35-mum 2P4M digital process and have a small chip area of 0.4mm². With the similar second order curvature correction adopted in conventional smart sensors, the achieved measurement error is within plusmn0.8degC over -40degC~95degC temperature range. The effective resolution is about 0.5degC with a 256-to-1 MUX. The power consumption is 9 muW at a sampling rate of 20 samples/s and a measurement rate as high as 1MHz is feasible