Current Clamp Circuit for Output Glitch Reduction in Test Systems
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Solution Overview
Problem
Automated test systems face issues with false indications of failures or masking actual failures due to sudden transitions in current ranges during testing, causing undesired glitches at test monitoring points.
Innovation Solution
The implementation of current clamp circuits within the output stages of the test circuitry, which allows for gradual and controlled transitions of output current between high and low current force amplifiers, thereby minimizing glitches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sudden transitions in current ranges are used during testing, then testing speed and productivity are improved, but output glitches occur causing false failure indications
Solution Approach 1:
The system performs preliminary actions by gradually pre-adjusting the current clamp level before switching between force amplifiers. This preliminary adjustment prevents sudden current transitions that cause output glitches, thereby maintaining both high productivity and reliable failure indication without requiring slow transitions during actual testing operations.
2Object-generated harmful factors
If gradual current transitions are used between force amplifiers, then output glitches are reduced, but testing speed decreases
Solution Approach 1:
The current clamp level is adjusted in advance before force amplifier switching occurs. This preliminary action prepares the current transition path ahead of time, allowing the actual switching to happen quickly without causing output glitches. The system achieves both glitch reduction and high productivity by separating the gradual adjustment phase from the switching phase.
Solution Approach 2:
The system dynamically changes the current clamp parameter before switching between force amplifiers. By adjusting this parameter in advance, the system controls the current transition characteristics without limiting the switching speed, thereby resolving the contradiction between glitch reduction and testing speed.
3Ease of operation
If current clamp level is adjusted during testing, then current transition control is improved, but additional control complexity is introduced
Solution Approach 1:
The control system automatically manages the current clamp level adjustments without requiring external intervention. The system self-regulates by detecting when force amplifier switching is needed and autonomously performing the preliminary current clamp adjustments, thereby improving ease of operation while keeping the control architecture manageable through automation rather than manual complexity.
Data Source
AI summary
A clamp circuit comprises an output transistor and a replica transistor coupled as a current minor pair, wherein the replica transistor is scaled in size to the output transistor by a size ratio; a first current source configured to set a current in the replica transistor, wherein the output current is set at a clamped output current value that is a sum of current of the first current source and a scaled value of the current of the first current source determined according to the size ratio; and a register circuit, wherein a register value stored in the register circuit sets the clamped output current value.