A Sensor to Detect Normal or Reverse Temperature Dependence in Nanoscale CMOS Circuits

The temperature dependence of MOSFET drain current varies with supply voltage. Two distinct voltage regions exist—a normal dependence (ND) region where an increase in temperature decreases drain current, and a reverse dependence (RD) region where an increase in temperature increases drain current. Knowledge of the temperature dependence is critical for avoiding overheating and wasted performance from excessive guardbands. In this paper, we present the first temperature dependence sensor to detect whether a system is operating in the ND or RD region. The dependence sensor occupies an area of 985 NAND2 equivalent gates. The sensor consumes 15.9 pJ per sample at a supply voltage of 1 V, with a 1°C resolution over the military-specified temperature range of -55°C to 125°C.