Problems with PN7412 contact interface

[GPTA]

Hello,
We've been using the PN7412 with the CCID program from the examples package for a while now. Everything was working smoothly until the tried out a new board design (our design), here the issue is : the PN7412 is unable to read the e

Here's the current status of the PN7412:
• Mass storage function is functioning properly.
• USB communication is working fine.
• It reacts as expected to changes in the RESET pin.
• LEDs connected to the GPIOs are operating correctly.
• It responds as expected to changes in the PRES pin.

However, it fails to read the eSIM (which is in the same board and the component itself is OK, we are able to read and interact with it using an external reader, our design comes with everything necessary to perform these tests, so we cant blaim the eSIM).

Upon further testing, I discovered that when the PRES pin is set to low, neither the VCC nor any other contact interface pins change their status. I conducted this test directly on the PN7412 using an oscilloscope, but the pins weren't outputting anything.

What's puzzling is that the connections for this board are the same as those used in our previous PCBs, where the PN7412 works perfectly (schematics attached), no major changes were applied this time in this new PCB version. I've also checked AN11738, and it seems that all the pins related to power are correctly configured.

What we have tested so far (tests conducted):
• Tested the eSIM with an external reader, and it responded correctly.
• Re-flashed the PN7412 that is not working with the same program as the other PN7412 units (the ones that work). However, the problems persist.
• Mounted another board (with the same design as the non-functional one) with a fresh PN7412, and encountered the same problem.
• We CAN read the eSIM using an external PN7412 (mounted on another board - a previous design we had), and it reads without a problem.
• Checked the behavior of the other PN7412 units (mounted on the older design boards) using the same oscilloscope, and the pins exhibited the expected behavior when attempting to communicate with a card.

So looks like :
* it is not the wiring/paths on the PCB
* it is not an issue with the eSIM
* it is not an issue with the SBC that interacts with the PN7412

We suspect that we are encountering a border condition or something that we have no clue , that may be interrupting the normal behavior of the NXP PN7412, we might be wrong, please your advise.

Do you have any suggestions as to why the pins aren't showing any activity? Any help or insights would be greatly appreciated.

[GPTA]

Hello Fabian,

Thanks for your quick response, and yeah the older designs boards can read the eSIM without problems.

About the IC swap, I already tested that, the new design board (aka the bad one) got an PN7412 with the markings:

7412AU-00
SPC667.1    05
ZSD19443

Which I swapped for one of the older IC we had with the markings:

7412AU-00
SPF917.1    01
ZSD20233

Sadly, I got the same bad behavior.

Now about the traceback, I will attach some of the readings I got with the oscilloscope. In the older design when I set the PRES to LOW, I got the behavior show in the image (Older_design_board.png), the blue reading is the VCC pin, and note that is the IC directly vs the oscilloscope, so the PN7412 is not receiving any response back.

On the other hand, in the new design I couldn´t get any reading, in none of the contact interface pin, as show in the image (New_design_board.png).

[Fabian_R]

Hello sir,
I'm very sorry but, this test is showing that the issue is caused by an unusual behavior in the board. Is there any chance that there are some differences that are causing the erratic behavior? Unfortunately, I will have to ask you to please take a deeper look at the PCB since I haven't detected any issue with the design of the board.
Is the IC drawing any current at some point?

[Fabian_R]

Hello, I've been assigned to support your case.
I appreciate your interest in our products.

According to your description, you have a previous design where the PN7412 works perfectly. In this design is it possible to connect the eSIM? And, perform an IC swap? I am interested in discarding the possibility of a bad PN7412 batch.
This will also help us to test the PRES pin to set it to low and, trackback the behavior.