A Study on the Characteristics of a Temperature Sensor with an Improved Ring Oscillator

This paper presents low power and high speed on-chip temperature sensor that uses only two ring oscillators which have different CMOS delay characteristics, counters and Time-to-Digital Converters (TDC) to maintain the performance benefit of the CMOS digital circuit. This novel temperature sensor does not require any bias circuits or external reference clocks. It measures the delay variations between the temperature-sensitive signal generator and the temperature-insensitive signal generator according to the temperature. The two ring oscillators were designed for the different gate channel length CMOS inverter. Additionally, the temperature-sensitive ring oscillator was stacked on the Cascode CMOS inverter. It generated two signals which were sensed by the TDC. However, temperature sensor of TDC cells, which was used to measure the delay time of two CMOS delay characteristics and convert to digital outputs, occupied a large chip area. To overcome this problem, we designed an advanced temperature sensor using Coarse-Fine TDC. We checked the performance of the temperature sensor using a HSPICE simulation.