Supply Glitch Detector Circuit Using Delayed Threshold Paths
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Solution Overview
Problem
Existing power glitch detection circuits, such as those described in U.S. Pat. No. 7,085,979B2, are limited by using a single power supply and resistor divider for glitch detection, making it difficult to distinguish between normal supply ripples and hacker-induced glitches.
Innovation Solution
A glitch detection circuit utilizing a glitch sense threshold generator that generates positive and negative glitch threshold signals through parallel paths with path delay circuits and comparators, operating in a stable analog domain to identify real hacker attacks by setting larger thresholds for glitches and lower thresholds for normal ripples, with adjustable sensitivity through trimmable resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single power supply and resistor divider are used for glitch detection, then the device complexity is reduced, but the measurement precision deteriorates making it difficult to distinguish between normal supply ripples and hacker-induced glitches
Solution Approach 1:
The detection circuit is segmented into multiple independent paths: a fast path that directly monitors voltage changes and a slow path that monitors voltage changes through an RC filter. This segmentation allows the system to differentiate between rapid hacker-induced glitches (detected by fast path) and normal supply ripples (detected by slow path), thereby improving measurement precision without significantly increasing overall device complexity.
Solution Approach 2:
An RC filter is introduced as an intermediary element in the slow path to delay and smooth voltage signals. This intermediary allows the circuit to compare the original voltage signal (fast path) with the filtered signal (slow path), enabling precise detection of abnormal voltage changes while filtering out normal ripple variations.
2Reliability
If a larger threshold is set to identify real hacker glitches, then the reliability of hack detection is improved, but the productivity deteriorates due to increased false negatives in detecting normal ripples
Solution Approach 1:
The detection system dynamically adjusts its response based on the characteristics of voltage changes. By using two paths with different response speeds, the system can adaptively distinguish between legitimate glitches requiring action and normal ripples that should be ignored, optimizing both reliability and productivity without fixed threshold limitations.
Solution Approach 2:
The system changes the monitoring parameters by creating two distinct detection paths with different time constants. The fast path captures rapid voltage changes with high sensitivity, while the slow path filters out high-frequency normal ripples. This parameter differentiation allows the system to maintain high reliability in hack detection while avoiding false positives that would reduce productivity.
3Ease of operation
If the glitch detection circuit operates in the digital supply domain, then the ease of operation is improved, but the stability deteriorates as the detection circuit becomes susceptible to the same glitches it aims to detect
Solution Approach 1:
An RC filter circuit serves as an intermediary between the digital supply domain and the detection logic. This intermediary stabilizes the detection process by filtering out high-frequency noise and glitches from the digital supply, allowing the detection circuit to operate stably while remaining integrated with the digital system.
Solution Approach 2:
The slow path creates a protected detection environment by filtering out harmful high-frequency glitches from the digital supply domain. This inert environment allows the comparison logic to operate stably and reliably, immune to the very glitches it is designed to detect, while maintaining ease of operation through direct digital domain integration.
Data Source
AI summary
A glitch detection circuit (200) is arranged detect a glitch on a digital supply (150) and comprises a glitch sense threshold generator (132), a path delay circuit (133) comprising two parallel paths, wherein the first path provides a first output of a slow signal path of the digital supply to be detected that is used as a positive glitch threshold signal (530) and the second path provides a second output of a slow signal path of the digital supply to be detected that is used as a negative glitch threshold signal (540). A comparator circuit (134) is arranged to compare the digital supply to be detected with the first output of a slow signal path and the second output of a slow signal path; wherein the output of the comparator circuit indicates a power glitch on the digital supply in response to the positive or negative glitch threshold signals.