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How is the PCB impedance tested?


Published by: April 09,2022

TDR testing is currently used primarily for PCB (printed circuit board) signal lines and device impedance testing.


                       How is the PCB impedance tested?


There are many reasons for affecting the accuracy of TDR test, mainly reflection, calibration, reading selection, etc. Reflex will cause serious deviation of the short PCB signal line test value, especially in the case of using TIP (probe) to test. Obviously, because the TIP and signal line contact points cause a large impedance discontinuity, the reflection occurs, and the impedance curve of the PCB signal line in the vicinity of three or four inches is fluctuating.


PCB impedance tests such as single-ended signal lines, differential signal lines, connectors, etc. This PCB impedance test has a requirement that is combined with the actual application conditions. For example, if the signal rising edge of the signal line is about 300 ps, then the rising edge of the TDR output pulse signal should be set at around 300 ps instead of Use a rising edge of about 30ps, otherwise the PCB impedance test results may be quite different from the actual application.

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