A 0.026 mm² Time Domain CMOS Temperature Sensor with Simple Current Source

Area of Science:

• Integrated Circuits
• Sensor Technology
• Semiconductor Devices

Background:

• Conventional temperature sensors often face challenges with linearity and die area.
• Simple current sources are desirable for miniaturization and power efficiency in integrated circuits.

Purpose of the Study:

• To present a time-domain CMOS temperature sensor with a simplified current source architecture.
• To achieve improved temperature linearity and a small active die area.
• To evaluate the sensor's performance in terms of accuracy, resolution, and energy efficiency.

Main Methods:

• Design of a time-domain CMOS temperature sensor utilizing a simple current source with an n-type poly resistor and a PMOS transistor.
• Implementation of a current-controlled oscillator using three current-starved inverter delay cells.
• Post-layout simulations in a 0.18 μm 1P6M CMOS process to assess performance.

Main Results:

• Achieved a small active die area of 0.026 mm².
• Demonstrated superior temperature linearity compared to conventional feedback-based approaches.
• Post-layout simulations showed a temperature error within -1.0 to +0.7 °C over 0-100 °C after two-point calibration.
• Attained a temperature resolution of 0.32 °C and a conversion rate of 50 kHz.
• Reported energy efficiency of 1.4 nJ/sample and supply voltage sensitivity of 0.077 °C/mV.

Conclusions:

• The proposed simple current source architecture offers enhanced temperature linearity and a compact design for CMOS temperature sensors.
• The sensor demonstrates excellent accuracy and efficiency, suitable for integrated sensing applications.
• This design provides a promising alternative to conventional temperature sensing methods, particularly where space and power are constrained.