Timing Margin Sensor Circuit for PVT Adaptation
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Solution Overview
Problem
Conventional sensors in digital integrated circuits are slow to respond to changes in PVT conditions, leading to potential timing violations and increased power dissipation due to the need for excessive timing margins.
Innovation Solution
A timing margin sensor circuit comprising a time-to-digital converter, predictor, and translation circuit that measures and adjusts clock frequency based on supply voltage and temperature changes, using tunable delay stages and averaging/selection mechanisms to prevent timing violations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional sensors are used to detect PVT conditions, then the circuit structure is simple, but the response speed is slow causing timing violations and increased power dissipation
Solution Approach 1:
The patent combines multiple delay stages with different sensitivity characteristics into a single sensor circuit that simultaneously measures both fast-changing and slow-changing PVT conditions. The first delay stage is sensitive to fast-changing conditions while the second delay stage is sensitive to slow-changing conditions, allowing the circuit to respond quickly to voltage changes without being affected by temperature variations, thereby achieving fast response speed without excessive complexity
Solution Approach 2:
Different delay stages are designed with different sensitivity characteristics to local PVT conditions. The first delay stage is specifically designed to be sensitive to supply voltage changes, while the second delay stage is sensitive to temperature changes. This local specialization allows each stage to optimize its response to specific conditions, improving overall sensor performance without requiring a completely complex redesign
2Reliability
If excessive timing margin is allowed to compensate for slow sensor response, then timing violations are prevented, but power dissipation increases and performance decreases
Solution Approach 1:
The clock frequency is dynamically adjusted based on real-time PVT condition measurements from the sensor circuit. The clock stretcher continuously monitors the output of the delay stages and adjusts the clock frequency accordingly, allowing the system to operate at maximum frequency when conditions permit while reducing frequency only when necessary to prevent timing violations. This dynamic adjustment eliminates the need for excessive static timing margins, thereby reducing power dissipation while maintaining reliability
Solution Approach 2:
The patent implements a feedback mechanism where the sensor circuit continuously monitors PVT conditions and feeds this information back to the clock stretcher, which then adjusts the clock frequency in real-time. This closed-loop control ensures that the clock frequency is optimized for current conditions, preventing timing violations without requiring excessive margin, thus reducing unnecessary power dissipation while maintaining system reliability
3Reliability
If clock frequency is reduced to prevent timing violations, then reliability is improved, but performance targets are not met
Solution Approach 1:
The clock frequency is dynamically adjusted based on real-time PVT condition measurements rather than using a fixed conservative frequency. The clock stretcher continuously monitors the sensor output and adjusts the clock frequency to the maximum safe level for current conditions, allowing the system to operate at high performance when PVT conditions permit while ensuring reliability when conditions deteriorate, thus meeting performance targets without sacrificing reliability
Data Source
AI summary
A timing margin sensor circuit includes one or more time-to-digital converters (TDCs), a predictor, and a translation circuit. The TDC(s) measure(s) progress of a clock signal through one or more chains of delay stages. The progress depends on sense conditions acting upon the delay chain, such as the supply voltage and the temperature. The predictor receives the measured progress. If the delay chain becomes slower, the predictor extrapolates a predicted progress value. If the delay chain becomes faster, the predictor outputs the actual progress value. The translator translates the predictor output value to sense information that can be used in a clock stretcher circuit. The timing margin sensor may further have an averager/selector to average or select from the results of multiple TDCs. The timing margin sensor may further have a calibrator to compensate for nominal sense conditions, and one or more tunable delays circuits.