Can Impedance change be affected by capacitors for ESD protection?

Thread Starter

Sungmin91

Joined Apr 2, 2024
3
I put the 1nF capacitor for ESD protection in the LIN interface node. After testing 6kV, impedance deterioration before and after was measured in the measurements. Does this mean that insufficient capacitance values are likely to be applied?
 

KeithWalker

Joined Jul 10, 2017
3,188
That is not much information to work with.
Did you connect the capacitor to anything? If so, to what?
Can you let us know how and what you did 6kV testing on?
What did you measure the impedance of and how did you do it?
With answers to all of those questions, we may be able to offer an opinion.
 

Thread Starter

Sungmin91

Joined Apr 2, 2024
3
Did you connect the capacitor to anything?
The LIN Bus is connected to the transceiver through the connector pin, and the capacitor is populated for ESD protection close to pin on PCB. I am on the test to check if the LIN transceiver's internal ESD protection and ESD protection capacitor are enough without any additional ESD component.

Can you let us know how and what you did 6kV testing on?
DUT was loaded with 6kV Contact Discharges on some test points.

What did you measure the impedance of and how did you do it?
I measured the line impedance between pin to GND from pre to post-test.
 

KeithWalker

Joined Jul 10, 2017
3,188
Did you connect the capacitor to anything?
The LIN Bus is connected to the transceiver through the connector pin, and the capacitor is populated for ESD protection close to pin on PCB. I am on the test to check if the LIN transceiver's internal ESD protection and ESD protection capacitor are enough without any additional ESD component.
You still have not explained exactly where you connected the capacitor. Is it decoupling the power supply? Is it connected across the data bus?

[/QUOTE]
Can you let us know how and what you did 6kV testing on?
DUT was loaded with 6kV Contact Discharges on some test points.
[/QUOTE]

What is the device under test? Where are the test points connected to on the DUT?

[/QUOTE]
What did you measure the impedance of and how did you do it?
I measured the line impedance between pin to GND from pre to post-test.
[/QUOTE]

What were the the results of your tests before and after doing the Discharges and before and after adding the capacitor?


Please bear in mind that we have no idea of what you are trying to do, how you are doing it or what results you are getting unless you tell us with enough detail for us to try to answer your question.
 

Thread Starter

Sungmin91

Joined Apr 2, 2024
3
Sorry, i try to explain more detail.
But, I already explained that the cap is connected to the LIN data line between the connector pin and the transceiver. For understanding I took arbitrarily the schematic from the datasheet,

1715163448984.png
Device has LIN interface connecting with LIN bus via cable. I inject ESD pulse contact to device case. Not applied directly to the pin, but applied to the screw part, at the corner of the case. And I compared impedance before and after discharge between pin to GND. And I measured the deterioration of the impedance of the LIN connector pin. Z [ohms] Diff Post - Pre [%] : -30.00%.
My question comes from whether this deterioration is caused by failure of capacitor value.

If right, I would like to discuss the parameters that should be considered, such as the recommended value of the cap satisfied with LIN signal integrity and ESD spec 6kV, and types such as C0G and X7R.
 

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KeithWalker

Joined Jul 10, 2017
3,188
The easiest way to check if the deterioration of the impedance is caused by capacitor failure is by replacing the capacitor with a known good one and measuring the impedance again. The rest of your questions can only be answered by the manufacturers of the TLIN1022.
 
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