Compact and Supply-Voltage-Scalable Temperature Sensors for Dense On-Chip Thermal Monitoring

Abstract

This paper presents compact and voltage-scalable temperature sensor circuits for implementing dynamic thermal management (DTM) in high-performance microprocessors and Systems-on-Chips (SoC). The proposed sensor front ends require only 6 to 8 NMOS transistors, resulting in more than one order of magnitude smaller area than the previous state of the art. The sensor supply voltage can be scaled down to 0.6 V, so it can be integrated with digital circuits employing a dynamic-voltage-scaling technique without additional power distribution and regulation. Sensor front ends with three different sizes (115, 279, and $400\;\upmu {\text{m}^2}$ ) and their back ends have been prototyped in a 65 nm CMOS technology. The measurement results of the $279\;\upmu {{\rm m}^{2}}$ front end at 0.6 V show a worst-case error of 7.0° C across 64 instances 0° C to 100° C after a low-cost one-temperature-point calibration. With the same conditions, the measurements of the $400\;\upmu {{\rm m}^{2}}$ front end show a worst-case error of 5.4° C across 64 instances. The compact sensor designs make it possible to integrate an order of magnitude more sensors on a chip with little additional overhead and thereby enable very dense thermal monitoring in digital VLSI systems.