Supply Glitch Detector Circuit Using Filtered Voltage Comparison
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Solution Overview
Problem
Circuits are prone to malfunction due to transient changes in supply voltage, known as glitches, which can be maliciously induced to disrupt logic circuitry operations.
Innovation Solution
A circuit arrangement that includes a low pass filter and two detector circuits, each comprising PMOS and NMOS transistors, to detect transient positive and negative changes in the supply voltage, generating detection signals that indicate glitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circuit operates with a supply voltage that can be maliciously changed, then the circuit can be manipulated to cause malfunction, but adding protection circuits increases device complexity
Solution Approach 1:
The detection function is segmented into two specialized detector circuits: one for detecting positive voltage glitches and another for negative voltage glitches. Each detector is optimized for its specific detection task, allowing the system to achieve comprehensive protection while maintaining manageable complexity through functional division
Solution Approach 2:
A low-pass filter is introduced as an intermediary component between the supply voltage and the detector circuits. The filter smooths out high-frequency noise and transient variations, allowing the detectors to focus on detecting genuine glitch conditions while filtering out spurious signals, thereby reducing false detections and simplifying the overall detection logic
2Measurement precision
If detector circuits are added to detect supply voltage glitches, then glitch detection capability is improved, but the circuit consumes more power
Solution Approach 1:
The detector circuits are designed to activate and generate detection signals only when glitch conditions are present. During normal operation, the detectors remain in a low-power state. This periodic activation based on detected events significantly reduces average power consumption while maintaining high detection precision when glitches occur
Solution Approach 2:
Each detector circuit uses transistors with specifically optimized parameters tailored to their detection function. The PMOS and NMOS transistors are configured with threshold voltages and dimensions that maximize detection sensitivity for their respective glitch types while minimizing leakage current and power consumption during normal operation
3Reliability
If the supply voltage changes transiently causing glitches, then logic circuitry malfunctions occur, but detecting and responding to these changes adds detection time
Solution Approach 1:
The detector circuits continuously monitor the supply voltage in advance, maintaining readiness to detect glitches without requiring additional response time when events occur. The low-pass filter pre-processes the voltage signal, preparing it for detection. This preliminary monitoring and signal preparation ensure that glitches are detected immediately upon occurrence, eliminating detection time delays
Solution Approach 2:
The detection mechanism replaces complex sequential analysis with direct electrical signal comparison. The detector circuits use transistor-based voltage comparison that occurs in parallel and simultaneously, rather than through sequential sampling or analysis steps. This electrical substitution of detection mechanics enables near-instantaneous glitch detection with minimal time loss
Data Source
AI summary
A circuit arrangement for detecting a glitch on a supply voltage comprising a low pass filter arrangement coupled to a supply terminal and configured provide a filtered supply voltage. The circuit arrangement comprises a first and second detector circuit each configured to receive the supply voltage and the filtered supply voltage and configured to provide a first and second detection signal indicative of a glitch comprising a transient, positive and a transient negative change in the supply voltage at a first detector output terminal and second detector output terminal respectively. The circuit arrangement further comprises a circuit-arrangement output terminal configured to provide an output signal indicative of the detection of a glitch in the supply voltage based on the first detection signal and the second detection signal.