Coaxial Impedance Transformer for CDM ESD Testing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current Charged Device Model (CDM) testing methods face challenges in accurately simulating the high-speed discharge currents due to variable resistances in air sparks and metal-to-metal contacts, which can lead to incomplete clamping of ESD threats by silicon protection circuits, and existing no-spark methods like the Contact CDM (CCDM) test fail to replicate the original CDM discharge impedance effectively.
Innovation Solution
A wide bandwidth, high-speed coaxial impedance transformer is used to reduce the test impedance between the Device Under Test (DUT) and the 50-ohm discharge circuit, simulating the CDM discharge impedance by gradually tapering the impedance of the coaxial transmission line, ensuring accurate peak current and voltage measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If air spark discharge or metal-to-metal contact is used in CDM testing, then the discharge current can flow to ground, but the variable resistance causes inconsistent peak current levels and incomplete clamping of ESD threats
Solution Approach 1:
The invention extracts and eliminates the variable resistance element (air spark or metal contact) from the discharge path by using a controlled impedance transmission line instead. This removes the source of inconsistency in peak current levels while maintaining the essential function of providing a discharge path to ground.
Solution Approach 2:
The invention changes the resistance parameter from variable (air spark/metal contact) to controlled and consistent (50-ohm impedance transmission line). This parameter change ensures repeatable peak current levels while maintaining the discharge function.
2Ease of manufacture
If a 50-ohm impedance is used in the discharge circuit, then the measurement system has standard impedance matching, but the impedance is too high to accurately simulate the low impedance of real CDM discharge events
Solution Approach 1:
The invention introduces an impedance transformation network as an intermediary between the 50-ohm measurement system and the low-impedance DUT. This mediator allows the high-impedance measurement system to accurately measure low-impedance discharge events by transforming the impedance levels while maintaining measurement accuracy.
Solution Approach 2:
The invention changes the impedance dimension by using a transmission line with characteristic impedance different from the measurement system impedance. This dimensional change in impedance space allows accurate simulation of low-impedance CDM events while using standard 50-ohm measurement equipment.
3Productivity
If the discharge path uses air sparks or metal contacts, then the discharge can occur, but the variable resistance prevents accurate and repeatable peak current measurements
Solution Approach 1:
The invention removes the variable resistance element (air spark or metal contact) from the discharge path and replaces it with a controlled impedance transmission line. This extraction eliminates the source of measurement inconsistency while maintaining fast discharge characteristics.
Solution Approach 2:
The invention changes the resistance parameter from variable to controlled, using a 50-ohm transmission line that provides consistent and repeatable peak current measurements while maintaining the high-speed discharge characteristics needed for CDM testing.
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
This approach allows for precise simulation of the CDM discharge waveform, minimizing reflections and achieving consistent peak current levels, thereby providing a reliable and accurate test of ESD protection circuits without air discharge variations.
Implementation Method 1
A wide bandwidth, high-speed coaxial impedance transformer is used to reduce the test impedance between the Device Under Test (DUT) and the 50-ohm discharge circuit, simulating the CDM discharge impedance by gradually tapering the impedance of the coaxial transmission line
Implementation Method 2
This approach allows for precise simulation of the CDM discharge waveform, minimizing reflections and achieving consistent peak current levels
Data Source
AI summary
An ESD tester transforms high speed pulses from s 50-ohm impedance to the optimum lower impedance necessary to simulate the Charged Device Model (“CDM”) test impedance. Direct connections to the device under test eliminates the variations in spark or contact resistance of the present test while transforming the test pulse impedances to the appropriate level. Direct device connections with controlled impedance current paths provide either internal device discharge or external test pulse testing to simulate the original test. The sparkless direct connection controlled impedance transformation is identified by its ability to simulate similar device failures at similar test voltage failure levels.