Leakage-Based Ring Oscillator Layout for On-Chip Hot-Spot Sensing
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Solution Overview
Problem
Existing temperature monitoring systems for integrated circuits are inefficient due to large chip area requirements, inaccuracy, and power inefficiency, particularly in detecting localized hot-spots which can lead to thermal runaway and catastrophic failure.
Innovation Solution
A digital ring oscillator (DRO) is used for in-situ temperature monitoring, which produces a digital oscillatory signal with a frequency that varies as a function of temperature, leveraging leakage current to determine temperature without adding to the chip's power overhead or requiring an analog to digital converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional temperature sensing solutions are used, then temperature measurement capability is provided, but chip area overhead becomes large
Solution Approach 1:
The patent changes the operating parameter of the ring oscillator from frequency-based temperature sensing to leakage current-based temperature sensing. By monitoring the leakage current that flows when the enable signal is deasserted, the system achieves temperature measurement with significantly reduced chip area, as the same ring oscillator circuit serves dual purposes: frequency generation and temperature sensing.
Solution Approach 2:
The ring oscillator circuit is designed to perform multiple functions: it generates the operating frequency for the digital circuit and simultaneously serves as a temperature sensor. By leveraging the inherent leakage current characteristics of the oscillator circuit, the patent eliminates the need for separate temperature sensing components, thereby reducing chip area overhead while maintaining temperature measurement capability.
2Measurement precision
If analog temperature sensing solutions are used, then temperature measurement is achieved, but power consumption increases
Solution Approach 1:
The system uses the natural leakage current that already exists in the ring oscillator circuit during normal operation to sense temperature. No additional power is required to activate a separate sensing mechanism, as the temperature information is extracted from the existing operational characteristics of the oscillator when disabled. This self-service approach eliminates additional power overhead for temperature sensing.
3Measurement precision
If localized temperature sensing is implemented, then hot-spot detection accuracy is improved, but chip area requirement increases
Solution Approach 1:
The patent transitions from using frequency as the sensing parameter to using leakage current as the sensing parameter. This parameter change enables localized temperature sensing with minimal area overhead, as the leakage current measurement can be performed using the same ring oscillator circuit that generates the operating frequency, eliminating the need for additional sensing hardware in each localized region.
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
The DRO-based temperature monitoring system provides accurate, localized temperature measurements with a smaller form factor than traditional solutions, reducing power consumption and chip area overhead, while enabling fine-grained temperature sensing and efficient processing thread management.
Implementation Method 1
The state nodes toggle states as a result of leakage current gated by the header transistors from the supply voltage through the inverters to the state nodes, and as a result of leakage current gated by the footer transistors from the state nodes through the inverters to ground. The frequency of the toggling is a function of the leakage currents, and the leakage currents are a function of a temperature of the digital ring oscillator.
Data Source
AI summary
Digital ring oscillators (DROs) are distributed throughout an integrated circuit die to achieve localized temperature sensing with a small form factor. A DRO can include cross-coupled inverters, header and footer transistors, and delay elements. Leakage current through the DRO causes a state of an internal node to toggle at a frequency that is a function of temperature of the DRO, which can depend on temperature of a nearby circuit (e.g., a processor). The integrated circuit die may include a controller that is coupled to the DROs. The controller can receive oscillatory digital signals produced by the DROs and control operation of the integrated circuit die based on temperatures indicated by the frequencies of the oscillatory digital signals.