Ring Oscillator Sensing for IC Leakage and Temperature Monitoring
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Solution Overview
Problem
Existing integrated circuits (ICs) face challenges in accurately measuring sub-threshold leakage current and temperature due to variations in process technology, leading to inefficiencies in power consumption and operational monitoring.
Innovation Solution
The integration of a ring oscillator circuit (ROSC) with a sub-threshold bias generator and electronic switches allows for precise measurement of leakage current and temperature by converting these parameters into measurable frequency changes, using a processor to determine operating conditions and stress levels based on oscillation frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional temperature sensors are used to measure IC temperature, then temperature monitoring is provided, but measurement precision is insufficient due to process technology variations
Solution Approach 1:
The patent changes the measurement parameter from direct temperature sensing to frequency measurement. The ring oscillator's oscillation frequency is measured, and temperature is derived from this frequency through calibration curves. This parameter transformation eliminates the direct impact of process technology variations on measurement accuracy, as frequency measurements are more stable and reproducible across different manufacturing processes.
Solution Approach 2:
The patent uses a ring oscillator circuit as an indirect sensor that copies or reflects temperature information through its oscillation frequency. Instead of using a dedicated temperature sensor that is sensitive to process variations, the ring oscillator serves as a proxy measurement tool whose frequency characteristics can be calibrated to accurately represent temperature while being less susceptible to manufacturing variations.
2Temperature
If ring oscillator frequency is used to determine temperature, then temperature sensitivity is achieved, but measurement precision is reduced due to process technology dependence
Solution Approach 1:
The patent implements a calibration process where reference frequency measurements are taken at known temperature points, and calibration curves are generated. These calibration curves serve as feedback to correct and refine the temperature determination from ring oscillator frequency measurements, compensating for process technology variations and improving measurement precision while maintaining temperature sensitivity.
3Measurement precision
If leakage current measurement is implemented, then sub-threshold leakage detection is provided, but device complexity increases
Solution Approach 1:
The patent makes the ring oscillator multi-functional by using it for both temperature sensing and leakage current measurement. The same oscillation frequency data can be interpreted to determine either temperature or leakage current depending on the calibration and operating conditions. This universality eliminates the need for separate dedicated measurement circuits, thereby reducing overall device complexity while maintaining precise leakage detection capability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient detection of leakage current and temperature, allowing for improved power management, predictive maintenance, and enhanced IC reliability by providing accurate real-time monitoring and data logging.
Implementation Method 1
measuring an oscillation frequency at an output of a ring oscillator (ROSC) circuit located in the IC proximate to the functional transistor; determining one or more operating conditions of the functional transistor based on the oscillation frequency of the ROSC
Implementation Method 2
Inverter delay normally increases with temperature, such that the ring oscillator frequency reduces with increasing temperature
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
Determination of one or more operating conditions (leakage current, temperature and/or workload) of a functional transistor in a semiconductor integrated circuit (IC). The functional transistor provides an electrical current, which is provided as an input to a ring oscillator (ROSC). The ROSC is located in the IC proximate to the functional transistor and has an oscillation frequency in operation. The one or more operating conditions of the functional transistor are determined based on the oscillation frequency of the ROSC.