troubleshooting of produced prototype: nrf9160

[David]

Hello,

I have developed 10pcs of one prototype with the nrf9160 SiP. 

I have some questions regarding some errors im having.

Regarding the SIM 1V8 driver VCC, for UICC interface, I am observing a fluctuation on this channel/voltage, from 0V -> 0.4 VDC, with approximately 1hz frequency.

What can cause this to happend, what is the normal behaviour of this channel when it is short-circuited with ground or something else/similar ?

My second question is regarding the attached image, im observing this on a few of my prototypes, im not able to upload any modem firmware to the SiP, any idea why?

Regards,

David

[Andreas]

Hi David,

 

It might seem like this is in some way related to your HW, either the PCB design or SiP internal. Have you been able to get it working if shorting the SIM traces past U8?

Just to be on the safe side, I am assuming your prototype is behaving normally otherwise? What voltage are you seeing on DEC0 (should be 2.2V)?

 

I will be forwarding internally to get someone who knows the SIM module to comment.

 

Best regards,

Andreas