nRF9160 not outputting 1.8V in "SIM_1V8" pin

[KN7702]

We have designed a custom board using the nRF9160. Most of the circuitry around nRF9160 is referencing the same as circuitry on the nRF9160 DK board. Upon flashing the modem firmware and the AT_Client sample application (with Bootloader), it seems that pin SIM_1V8 does not output 1.8V at all. 

I have noticed we have SIM_DET routed to our Sim Card Tray switch for switching between eSIM and SIM, but I have cut the trace since. The SIM_DET is now floating. 

The nRF9160 is powered from a 3.3V source and the ENABLE pin is at 3.3V (nRESET is also pulled high to 3.3V) and I can flash it with the Segger J-Link programmer, but the internal 1.8V regulator seems to be not operational. 

I understand there was a similar ticket before and it was resolved by reflowing the board. I could understand one or two boards might have reflow issue, but I have all of the boards exhibiting the same issue. 

Any help would be appreciated. 

[Håkon Alseth]

Hi,

 

The SIM_1V8 is only supplied when the SIM needs to be communicated with.

The modem provides AT commands for verifying if the SIM communication is OK or not:

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/access_uicc/xsim.html?cp=2_1_12_0

 

If you run at_client + nRF Connect for Desktop, LTE Link Monitor, and issue these commands:

at+cereg=5
at+cfun=1
at+cfun?

Could you share the log output from running this?

 

Kind regards,

Håkon

[KN7702]

Sorry for the delay, it took some time to get it setup. Here's the response I received from my terminal:

at+cereg=5
OK
\n
at+cfun=1OK
\n+CEREG: 90
\n
at+cfun?+CFUN: 1
\nOK
\n

Originally upon power on, I tested it with at+cfun?, it response with 0. 

However, when I input the commands as suggested, it seems to enable the LTE modem but I have yet to measure the 1.8V from the internal regulator. Am I still missing something?

[Håkon Alseth]

Hi,

 

CEREG: 90 means that it has problems communicating with your SIM:

https://infocenter.nordicsemi.com/topic/ref_at_commands/REF/at_commands/nw_service/cereg_read.html

Please check your soldering and the overall connection towards the SIM card.

 

Do you see this on several boards, or just one?

 

Kind regards,

Håkon