Calibration of Ring Oscillator-Based Integrated Temperature Sensors for Power Management Systems.

Area of Science:

• Integrated circuit design
• Sensor technology
• Semiconductor device physics

Background:

• Accurate thermal monitoring is crucial for System-on-Chip (SoC) performance and reliability, especially in DC-DC converters.
• Traditional temperature sensing often relies on trimming, which adds complexity and cost to integrated circuit manufacturing.
• Process variations in semiconductor fabrication can significantly impact sensor accuracy.

Purpose of the Study:

• To develop and validate a trimming-free temperature sensing methodology for integrated circuits.
• To investigate calibration techniques that mitigate process variations for accurate temperature-to-frequency mapping.
• To offer a cost-effective and efficient alternative to traditional trimmed temperature sensors.

Main Methods:

• Implementation of an untrimmed oscillator-based integrated sensor in a 0.18-μm SOI XFAB process.
• Characterization of the quadratic relationship between oscillator output frequency and temperature.
• Development and evaluation of multiple trimming-free calibration techniques, including Corrected One-Point, Two-Point, and Three-Point methods.

Main Results:

• A quadratic relationship between oscillator frequency and temperature was identified and utilized for calibration.
• The Corrected One-Point calibration method achieved a maximum error of ±2.95 °C without requiring a temperature chamber.
• Two-Point and Three-Point calibration methods demonstrated high precision, with R2 values of 0.9958 and 0.9956, respectively.

Conclusions:

• Competitive temperature sensor calibration results are achievable without circuit trimming.
• Trimming-free calibration techniques offer a viable alternative or complementary approach to traditional methods.
• The proposed methodology enhances thermal monitoring capabilities in SoC applications, particularly for DC-DC converters.