Comparator Signal Masking Circuit for Glitch Blocking
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Solution Overview
Problem
Noise switchings in digital signals generated by comparators can cause improper operation in systems like phase-locked-loop circuits, due to rapid succession of spurious noise events, such as glitches, which jeopardize the entire system's operation.
Innovation Solution
A protection circuit that includes a comparator, a state-change detection circuit, and a switching-inhibition mechanism to inhibit further switchings of the output signal for a defined time interval after a change, using a masking circuit with a flip-flop and delay circuit to maintain the output signal state for a set period, thereby preventing noise switchings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a comparator is used to generate digital signals, then signal comparison and conversion capability is improved, but noise switchings and glitches are introduced that cause improper system operation
Solution Approach 1:
A masking circuit is introduced as an intermediary between the comparator and the output to filter out noise switchings. The masking circuit receives both the digital signal from the comparator and a masking signal, and only allows the digital signal to pass through when the masking signal permits, thereby eliminating spurious noise events while preserving the valid comparison results
Solution Approach 2:
The masking signal is generated in advance based on the differential input signal before the comparator output is finalized. By predicting when valid transitions will occur and pre-enabling the output during these periods, the system prevents noise switchings from reaching the output while maintaining accurate signal comparison capability
2Reliability
If noise protection masking is applied to eliminate noise switchings, then system reliability is improved, but signal response time increases due to masking duration
Solution Approach 1:
The masking is applied partially rather than continuously - the masking circuit allows signals to pass through during valid transition periods when the masking signal permits. By applying masking only when necessary to prevent noise switchings and not during valid signal periods, the system achieves noise protection without excessive time loss
Solution Approach 2:
The masking circuit dynamically adjusts its blocking behavior based on the state of the masking signal and digital signal. The circuit transitions between blocking and passing states in real-time, enabling fast response to valid signals while maintaining protection during vulnerable periods, thus optimizing both reliability and response time
Data Source
AI summary
A method of protection from noise of a digital signal generated by a comparator, including the steps of generating an output signal that switches from a first logic state to a second logic state at a first switching of logic state of the digital signal; detecting a change from the first logic state to the second logic state of the output signal; and inhibiting further switchings of the output signal for a first time interval after the change from the first logic state to the second logic state.