nRF 9160 - ESD for SIM signals

SilasValera

So nice to be part of this community!
I am working on the schematic to use nRF9160 into my devices after running some tests successfully (thanks for your help there🙂, Referring the schematic of nRF Feather, it seems there is no ESD chip used for the SIM signal lines. Is that ok? Since my devices will be in the field, may it is better I use that?
Thank you!!
Silas V

jaredwolff

Glad you're here SilasValera! 🙂

An ESD chip is always a good idea. If you're designing something that needs to be rock solid during use, especially if you're changing out a removable SIM, even more of a good idea.

Overall, it depends on your level of comfort and how often you see yourself switching out the SIM. Also take in to account your operating environment. Is it going to be dry and prone to static discharge? Another vote for some type of ESD protection for a removable SIM.

Hope that helps with your decision!

jaredwolff

SilasValera what firmware are you running? Still your application firmware? What are the values if you run at 3.5VDC on VBAT? I assume the first numbers are the identifiers for the boards?

piotr337 I ran a quick test with a different board, and that worked, then I switched back the “bad” board and it fails.

Gotcha thanks for checking. Are you strictly using the bootloader only? Is it possible you may have overwritten the bootloader?

I believe the default configuration for the newer boards is reverse the polarity that it should be for >= v5. Meaning that if you initialize the LED without those changes it’s on by default. i.e. that may not be the bootloader running but another application

SilasValera

Thank you so much Jared! You have cleared my mind🙂 I will go with adding ESD chip.

best
Silas V