Integrated Characterization Circuit for Supply Voltage Histograms
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Solution Overview
Problem
Existing methods for monitoring supply voltage variations in integrated circuits are inaccurate due to complexities in load variations, clock frequency changes, and limitations in observing high-frequency changes, especially when the circuit dynamically changes modes.
Innovation Solution
An integrated circuit with a characterization circuit that samples and holds supply voltage within a short time frame, using a small and low-power ADC to capture histograms of supply voltage magnitudes near the semiconductor die, allowing for accurate measurement of the power supply network and supporting mode-specific observations with optional blackout intervals and zoom features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast ADCs are mounted on the circuit board to measure supply voltage in real time, then measurement speed is improved, but measurement precision deteriorates due to package parasitics blocking high-frequency observations at the semiconductor die
Solution Approach 1:
A sample/hold circuit is introduced as an intermediary component between the supply voltage source and the ADC. This circuit captures instantaneous voltage samples during a short window and holds them for the ADC to convert, enabling accurate high-frequency measurement without requiring the ADC to be physically located at the semiconductor die. The sample/hold circuit acts as a buffer that decouples the timing requirements of sampling from the conversion process.
Solution Approach 2:
The measurement function is segmented into two distinct stages: (1) a fast sample/hold stage that captures instantaneous voltage during a short time window, and (2) a slower ADC conversion stage that processes the captured sample. This segmentation allows the system to achieve high effective sampling rates without requiring ultra-fast ADCs, resolving the contradiction between measurement speed and precision.
2Device complexity
If ADCs are placed external to the semiconductor die for easier access, then device complexity is reduced, but measurement precision deteriorates due to inability to observe high-frequency voltage changes at the die location
Solution Approach 1:
The measurement system is divided into two functional segments: a fast sample/hold circuit that can be placed close to or on the semiconductor die to capture high-frequency voltage transients, and a slower ADC that can be located externally where it is more accessible. This spatial and functional segmentation allows each component to be optimally positioned without compromising overall measurement precision.
Solution Approach 2:
The sample/hold circuit serves as an intermediary that bridges the gap between the internal high-frequency voltage environment at the die and the external ADC. It captures the instantaneous voltage state and transfers it to the external ADC for conversion, enabling precise measurement of high-frequency variations without requiring the ADC to be physically embedded in the die.
3Measurement precision
If a large ADC is used to capture supply voltage variations accurately, then measurement precision is improved, but area occupied increases
Solution Approach 1:
The measurement task is segmented between the sample/hold circuit (which occupies minimal area) and the ADC. By performing the high-speed sampling function in the sample/hold stage, the ADC can be a smaller, lower-resolution device that only needs to convert already-captured voltage samples, significantly reducing the total area required while maintaining measurement precision.
Solution Approach 2:
The sample/hold circuit performs the time-critical sampling function partially (during a short window), allowing the ADC to complete the measurement process at a slower pace. This partial action approach enables the use of a smaller ADC that would be insufficient for direct high-speed sampling but is adequate for converting the pre-captured samples with high precision.
4Adaptability or versatility
If mode changes are supported dynamically during operation, then adaptability is improved, but measurement precision deteriorates due to spurious samples during transition periods
Solution Approach 1:
The system performs preliminary actions by detecting mode change events and initiating blackout intervals before spurious samples can corrupt the histogram data. The blackout interval is proactively implemented during transitions, preventing inaccurate samples from being captured and added to the histograms, thereby maintaining measurement precision while supporting dynamic mode changes.
Solution Approach 2:
The system uses feedback from mode change detection to control the sampling process. When a mode change is detected, the system automatically activates blackout intervals to pause sampling, ensuring that histograms are not contaminated with spurious data. This feedback mechanism allows the system to adapt to mode changes while preserving measurement integrity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Provides accurate, real-time monitoring of supply voltage behavior across different modes without constraining workload, enabling optimized power supply design and voltage management, reducing spurious samples during mode changes.
Implementation Method 1
a sample/hold circuit that may sample the supply voltage in a short window of time (e.g. within a clock cycle of the first circuit)
Implementation Method 2
an ADC that is configured to converge to the sampled voltage over a longer period of time (e.g. multiple orders of magnitude longer than the short window for the sampled voltage)
Implementation Method 3
capture a histogram of the supply voltage magnitude during operation of the integrated circuit
Data Source
AI summary
In an embodiment, an integrated circuit includes a first circuit and a characterization circuit to capture a histogram of the supply voltage magnitude to the first circuit (or other characteristics of the first circuit). In various embodiments, the characterization circuit may: be located near the first circuit; include a sample/hold circuit that may sample the supply voltage in a short window of time and an ADC that is configured to converge to the sampled voltage over multiple orders of magnitude longer than the short window; be relatively small and low power; capture multiple histograms, e.g. one for each mode of the first circuit; support a blackout interval during mode changes; support a zoom feature to a subrange of supply voltage disabled with fine-grain histogram buckets; and/or include one or more comparators to detect maximum and/or minimum voltages experienced over a time interval.