Temperature threshold sensors facilitate temperature protection in microprocessors by indicating when the processor gets overheated or too cold. This thesis presents a BJT based temperature sensor with a programmable temperature threshold from -40°C to 150°C. Comparison of a CTAT voltage with a PTAT voltage gives a one-bit digital output when the temperature of the die exceeds the set threshold. This work achieves a temperature detection accuracy of ±0.75°C, leading to the lowest reported relative inaccuracy among temperature switches by using a room temperature digital trim and without the use of any dynamic techniques. The design has a current consumption of 7uA, and the estimated area of the system is less than 0.05mm2 in 0.16µm CMOS technology.