Abstract
Due to the advance in CMOS technology and design complexity, more power is dissipated in smaller die area, thus the thermal density of modern VLSI systems is becoming a critical issue. High die temperature can not only degrade circuit performance but also leads to thermal runaway. Therefore, continuous monitoring of die temperature is crucial. In this thesis, a CMOS smart temperature sensor without conventional ADC or bandgap reference is proposed for thermal management of VLSI system. The accuracy is within ±0.8 °C over the temperature range of 0 °C to 125 °C after two-point calibration. The sensor consists of a □VGS generator that utilizes the temperature characteristics of CMOS transistors, a voltage-to-time converter and a time-to-digital converter to provide digital output. A small die area of 0.05 mm2, an extremely low power consumption of 120 □W and a high conversion rate of 3K conversion/s make this temperature sensor very suitable for VLSI integration. The sensor features a finest resolution of 0.025 °C/LSB with a 100 MHz external reference clock. In addition, the proposed temperature sensor is integrated into an on-line thermal monitoring scheme to verify its performance. Simulation shows that the circuit is under continuous monitoring of the proposed temperature sensor. If the die temperature reaches a certain limit, the on-line thermal monitoring will invoke supply voltage scaling to decrease the circuit power dissipation, thus the die temperature will decrease to a constant stable value.