Metastability-Resilient Data Synchronizer Circuit
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Solution Overview
Problem
Conventional methods for synchronizing asynchronous data signals with a clock signal are unreliable, particularly in high-speed digital systems, as they often result in metastability, which can cause circuit malfunctions, and are not effective under all technological conditions, including FinFET technologies.
Innovation Solution
A data synchronizer that includes an input circuit, pass gates, inverters, and a gate controller, which keeps the pass gates partially open during metastability and closes them when the capture nodes resolve to opposite logic states, ensuring reliable registration of the data signal into a clock domain, without relying on adjusting transistor size or drive strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two registers are coupled in series to synchronize asynchronous data signals, then the reliability of signal registration is improved, but the device complexity and latency increase
Solution Approach 1:
The patent introduces a specialized synchronizer circuit as an intermediary component between the asynchronous data signal source and the clock domain. This synchronizer includes a metastability detection mechanism that actively monitors capture nodes and controls pass gates to maintain signal integrity during transitions, thereby achieving reliable synchronization without requiring multiple series registers.
2Reliability
If additional registers are added in series to reduce metastability probability, then the reliability is improved, but the latency increases significantly
Solution Approach 1:
The synchronizer circuit performs preliminary action by proactively detecting metastable conditions before they propagate through the system. The metastability detection mechanism monitors capture nodes in advance and preemptively controls pass gates to prevent incorrect signal registration, eliminating the need for multiple delay stages and reducing overall latency.
3Speed
If conventional synchronization methods are used in high-speed systems, then the device operates at high speed, but metastability causes malfunctions
Solution Approach 1:
The patent implements a feedback mechanism where the synchronizer continuously monitors the state of capture nodes and adjusts pass gate control signals in real-time. This feedback loop detects metastable conditions as they occur and dynamically responds to maintain signal integrity, enabling reliable operation at high speeds where conventional fixed-timing methods fail.
4Difficulty of detecting and measuring
If transistor size or drive strength is adjusted to detect metastability, then the detection capability is improved, but the manufacturing complexity and adaptability to new technologies decrease
Solution Approach 1:
The synchronizer circuit employs a universal metastability detection mechanism that functions independently of specific transistor characteristics or technology nodes. The detection is based on voltage level monitoring and timing relationships rather than device-specific parameters, making the circuit adaptable to various technologies including FinFET and future process nodes without requiring manufacturing adjustments.
Data Source
AI summary
A data synchronizer that registers an input data signal into a clock domain of a clock signal. The data synchronizer includes in input circuit, first and second pass gates, first and second inverters, gate controller, and a register. The input circuit drives first and second data nodes to opposite logic states based on the input data signal. Each pass gate is coupled between a data node and a capture node. The inverters are cross-coupled between the capture nodes. The gate controller is capable of keeping the pass gates at least partially open during a metastable condition of the capture nodes, and closes the pass gates when the capture nodes resolve to opposite logic states. The register registers a capture node to provide a registered data output in response to the clock signal. The data synchronizer may be implemented using FinFET devices.