Low-Power Frequency-Mode Temperature Sensing Circuit with Subthreshold Operational Amplifier

This paper introduces a low-power frequency-mode temperature sensor. To increase the temperature detection range and maintain the high sensitivity of conventional frequency-mode temperature sensors, a negative feedback loop using an OPA is required, which leads to higher power consumption. To reduce the power consumption, this paper proposes an operational amplifier operated in the subthreshold region to realize the control loop. The proposed design is carried out with a 0.18-μm HV process. The simulated sensitivity is 289.1 nA/°C, and the detection error is -0.91°C to +0.99°C over the temperature range from -50°C to 170°C. Simulation results show that the power consumption is reduced by a factor of 2.5 while maintaining a high temperature detection range and sensitivity.