Edge Triggered Calibration for Semiconductor Test Systems
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Solution Overview
Problem
Existing test systems for semiconductor devices face inaccuracies due to differences in propagation delays between rising and falling edges of signals, which can lead to malfunctions, especially at high frequencies, as conventional calibration techniques adjust for average delays rather than edge-specific delays.
Innovation Solution
The implementation of edge-triggered delay measurement circuitry that selectively measures and adjusts the delays for rising and falling edges separately, using an edge-triggered element and a period measuring element to form a loop and measure propagation delays, allowing for precise calibration of circuit paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional calibration techniques adjust for average delays, then the calibration process is simple, but the measurement precision deteriorates due to inability to distinguish rising and falling edge delays
Solution Approach 1:
The calibration circuit segments the delay measurement into two independent paths: one for rising edges and one for falling edges. The multiplexer selectively connects different delay elements to the measurement circuit based on the edge type, allowing separate calibration of rising and falling propagation delays without requiring separate complete calibration circuits for each edge type.
Solution Approach 2:
The calibration circuit uses dynamic switching via multiplexer to reconfigure the measurement path based on the trigger edge type. The circuit transitions between measuring rising edge delays and falling edge delays by changing the connection state of the multiplexer, enabling a single circuit to adaptively measure different delay characteristics.
2Reliability
If edge-specific delay calibration is implemented, then the reliability of testing improves, but the device complexity increases due to additional circuit elements
Solution Approach 1:
The calibration circuit achieves multi-functionality by using a single measurement circuit that can measure both rising edge delays and falling edge delays through selective configuration. The multiplexer allows the same delay measurement circuitry to serve dual purposes by switching between different delay elements based on the edge type being measured.
Solution Approach 2:
The circuit changes the measurement parameter dynamically by selecting which edge type to measure. The multiplexer switches between different delay elements corresponding to rising and falling edges, allowing the measurement system to adapt its parameters (which delay to measure) based on the testing requirements without requiring separate dedicated circuits.
3Manufacturing precision
If average delay calibration is used, then the ease of operation is maintained, but the manufacturing precision deteriorates due to propagation delay differences affecting test accuracy
Solution Approach 1:
The calibration process is segmented into edge-specific measurements where rising edge delay and falling edge delay are measured and calibrated separately. This segmentation allows precise adjustment of timing for each edge type independently, ensuring that test signals are accurately timed regardless of which edge type is being used in the actual testing.
Data Source
AI summary
Circuitry for measuring a propagation delay in a circuit path. The circuitry includes a one-shot edge triggered element that can be connected in a loop with the circuit path. An edge signal propagating through the circuit path triggers the one-shot element to output a pulse. The pulse propagates around the loop, again triggering the one-shot element to produce a pulse, creating a repeating series of pulses. The period between these pulses is influenced by propagation time of an edge through the loop such that a difference in the period with the circuit path connected and not connected in the loop indicates propagation delay in the circuit path. Such circuitry can be configured to independently measure, and therefore calibrate for, propagation delays associated with rising and falling edges. Calibration to separately equalize propagation delays for rising and falling edges can increase the timing accuracy of an automatic test system.