Voltage Supply Droop Detector Using Delay Line Mismatch
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Solution Overview
Problem
Integrated circuits face challenges in detecting power supply droops, which can cause erroneous operations due to temporary voltage drops, making it difficult to determine the cause and characterize such failures.
Innovation Solution
A power supply droop detector is implemented with a delay unit and transition circuit that compares signal timing, using a calibration routine to adjust delay elements and detect mismatches indicative of voltage droops, distinguishing between transient and persistent causes like temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a delay unit with multiple delay elements is used to detect voltage droops, then the ability to detect and characterize power supply droops is improved, but the device complexity increases
Solution Approach 1:
The delay unit is divided into multiple delay elements (e.g., five delay elements) that can be selectively activated. This segmentation allows the system to create different delay paths and compare timing relationships to detect voltage droops, while maintaining manageable complexity through modular design
Solution Approach 2:
The detector uses feedback mechanisms where the output of the delay unit is fed back to the input, forming a ring oscillator during calibration. This feedback path enables automatic timing adjustment and calibration of the delay elements, improving measurement precision without requiring complex external calibration equipment
2Measurement precision
If a calibration routine with ring oscillator is implemented, then the timing accuracy of the delay unit is improved, but the startup time and calibration duration increase
Solution Approach 1:
The calibration routine is performed during system startup or initialization, before the actual droop detection begins. By conducting the ring oscillator calibration preliminarily, the timing accuracy is established in advance, allowing for rapid droop detection without repeating the lengthy calibration process during operation
Solution Approach 2:
The ring oscillator performs periodic oscillations during calibration, cycling through a predetermined number of periods. This periodic action allows the system to measure timing characteristics over multiple cycles, improving accuracy through averaging while limiting the total calibration time to a fixed number of periods
3Ease of manufacture
If the delay unit uses an odd number of inverting delay elements, then the ring oscillator formation during calibration is simplified, but the detection capability for different droop causes becomes more challenging
Solution Approach 1:
Different regions or elements within the delay unit are configured with different characteristics. By using an odd number of inverting delay elements, the ring oscillator forms naturally during calibration, simplifying the calibration process. The local quality differences in delay elements enable differentiation between transient and persistent droop causes through pattern recognition
Data Source
AI summary
A built-in self-test (BIST) circuit for detecting power supply droops is disclosed. In one embodiment, the BIST circuit includes a transition circuit configured to launch logical signals into a delay line. The BIST circuit also includes a comparator configured to compare a logic signal based on that input into the delay line with one output from the delay line. A mismatch resulting from the comparison is indicative of a power supply droop. The BIST circuit may also include circuitry for calibrating the delay line. The calibration may be performed by enabling a feedback path between the output of the delay line and its input. Enabling the feedback path may form a ring oscillator utilizing the delay line. A counter may count the number of transitions caused by the ring oscillator in a predetermined time. The resulting count may be used to determine if the delay is in a desired range.