Miniaturized BJT-Based Thermal Sensor for Microprocessors in 32- and 22-nm Technologies

A thermal sensor is proposed for microprocessors, which compares the BJT voltage to a reference by converting both voltages to frequency and dividing the frequencies to result in a digital number. The sensor has an rms resolution of ±0.2C and an area of 0.02 mm² at the 32-nm process node and 0.006 mm² at 22 nm, including all digital processing circuitry. The conversion rate is between 2-20 kS/s, which enables it to capture fast transients on the CPU. It consumes 3.8/1.4 mW at 32/22 nm from an unregulated 1.4-V supply. The combination of speed, low power, and area make this sensor appropriate to measure hot-spots in microprocessors.