Pulse Circuit Transmission Line Parasitic Pulse Blocking
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Solution Overview
Problem
Conventional Transmission Line Pulse (TLP) test systems face issues with parasitic pulses of opposite polarity damaging devices under test due to impedance mismatches, leading to premature failure during ESD characterization, as existing solutions either fail to effectively block these pulses or require high-voltage diodes with slow turn-on times and high parasitic capacitance, which are not suitable for very short pulses.
Innovation Solution
A pulse test circuit incorporating a selective pulse blocking module, comprising a diode in series with the signal path, which acts as an 'open circuit' for negative pulses and 'through connection' for positive pulses, effectively blocking parasitic pulses and preventing damage to the device under test, while allowing the main test pulse to pass through without distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a diode is used to block parasitic pulses, then parasitic pulses of opposite polarity are blocked, but high-voltage diodes have slow turn-on times and high parasitic capacitance which are not suitable for very short pulses
Solution Approach 1:
A transmission line is introduced as an intermediary component between the pulse source and the device under test. The transmission line exploits impedance mismatch at its open end to reflect parasitic pulses back toward the source, preventing them from reaching the DUT. This mediator approach allows blocking of harmful reflected pulses without requiring a diode directly at the DUT location, thereby avoiding the slow turn-on time and high parasitic capacitance issues of high-voltage diodes.
2Reliability
If impedance matching is used to prevent reflections, then signal integrity is improved, but parasitic pulses of opposite polarity are still generated due to nonlinear device behavior
Solution Approach 1:
The invention converts the harmful effect of impedance mismatch into a beneficial one. Instead of trying to eliminate all impedance mismatches (which would require perfect matching throughout the entire system), the invention intentionally utilizes the impedance mismatch at the open end of the transmission line to reflect parasitic pulses back toward the source. The mismatch that would normally cause harmful reflections at the DUT is instead positioned and controlled to reflect pulses away from the DUT, turning a potential harm into a protective mechanism.
3Object-affected harmful factors
If high-voltage diodes are used to block reflected pulses, then parasitic pulses are blocked, but the diodes require long recovery times which distort very short test pulses
Solution Approach 1:
The transmission line serves as an intermediary that handles the blocking function through impedance-based reflection rather than requiring a diode with fast switching characteristics. By positioning the transmission line's open end at a specific location, parasitic reflected pulses are automatically redirected back toward the source before they can reach the DUT. This eliminates the need for high-voltage diodes entirely, thereby eliminating the problem of long recovery times distorting very short test pulses.
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
The solution effectively eliminates parasitic pulses of opposite polarity, preventing damage to the device under test and allowing for accurate characterization of ESD protection devices using very short pulses with fast rise times, without the limitations of high-voltage diodes with slow turn-on times and high parasitic capacitance.
Implementation Method 1
a diode in series with the signal path, which acts as an 'open circuit' for negative pulses and 'through connection' for positive pulses
Implementation Method 2
Pulse reflections can occur in the TLP system due to changes in the signal line impedance, for example at one end of the transmission line
Data Source
AI summary
A circuit is provided wherein a test pulse is provided to a device under test. A module allows the test pulse to pass through to the device under test. The module blocks a reflected pulse from passing through to the device under test when the reflected pulse has an opposite polarity from the polarity of the test pulse. In some cases, the reflected pulse may be detrimental to the device under test if it is not prevented from reaching the device under test. In one embodiment, when a second reflected test pulse is traveling away from the device under test, the module allows the second reflected test pulse to pass through.