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,

 

Another thing, looking at the pictures, you have cut SIM_1V8 between J7/U8 and nRF9160, but from the second picture you are measuring SIM_1V8 at pin 2 of J7. Fair enough. But looking at the layout I am not seeing how this pad/net is connected to the SIM_1V8 from the SiP, that is only fed into the VCC pin:

Is there any external strap, internal layers or anything that I am missing?

 

Best regards,

Andreas