Ultra-Miniature 0.003 mm2 PNP-Based Thermal Sensor for CPU Thermal Monitoring

Miniaturized, integrated thermal sensors are utilized to measure hot and cold spots in CPU's in multiple locations and are critical for the power/performance of the chip. In this paper we report an ultra-miniature, 0.003 mm2, PNP thermal sensor in TSMC 65nm. The sensor utilizes a novel switched-capacitor bandgap reference and a single bit sigma-delta modulator to achieve a maximum error of ±1.35°C and a resolution of 130mK for a 12 bit, 4ms conversion. The sensor is the smallest reported BJT bandgap-based sensor, especially when considering the process node, and one of the smallest in all mechanisms. It has a competitive accuracy and resolution compared to compact bandgap-based sensors which can meet the CPU area specifications (< 0.02 mm2).