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

[Didrik Rokhaug]

Hi, and sorry for the long wait.

I have talked to one of our hardware experts, and there are some differences between your design and our reference designs:

You are missing a 47uF capacitor on IO_supplyu/DEC0.

The recommended value for the DEC0 decoupling capacitor has been increased to 47 uF. This is done to improve low-frequency clock accuracy which improves protocol robustness in lower limit temperature conditions. No issues have been observed in practical use on boards with lower values, but 47 uF is expected to perform better over conditions and production variation.

When it comes to your SIM interface, the differences between your SIM interface and ours is that C17 = 1uF instead of 100nF and C16 = 1uF instead of 10nF.

Do these changes solve your problem?

Best regards,

Didrik

[Pertti Kasanen]

I’m curious about this 4,7uF -> 47uF recommendation. We consider adding it to our new version (one that we want to work well outdoors in the Scandinavian winter climaate). 

This has not been included in the new reference desing files or in the Hardware Integration Guide 1.2. Is this 47uF still a valid recommendation (with the new Rev 2 B1A SoC)?

[Andreas]

Hi,

 

Rev 2 of the SiP has this reverted back to 4.7µF, so for future designs I would use 4.7µF, not 47µF. Rev1, in case you end up using that, will in most cases work just fine with 4.7µF also.

 

Best regards,
Andreas