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

Abstract

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).