An ultra low-power low-voltage programmable temperature detection circuit

The design of a low-power low-voltage programmable temperature detection circuit is described. The circuit provides a digital output that signals over-temperature and under- temperature conditions when die temperature rises above or falls below the programmed temperature thresholds. The output is obtained from the comparison between two temperature- related signals; the former has a CTAT with fixed thermal coefficient and the latter has an adjustable (PTAT, ZTAT or CTAT) thermal coefficient. The circuit design employs current as the main variable, based on the concept of inversion level. The circuit has been implemented in a 0.25μm standard CMOS process, operates down to 1.5V, occupies an area of 0.0235mm², consumes 750nA including bias circuitry, and has ±5% accuracy for threshold temperatures ranging from -40°C to 150°C.