nRF9160 bottom current difference

[Jayant Tang]

Hello DevZone,

One of our key customers is preparing to move their 9160 project into the mass production phase. Recently, they have raised a couple of questions regarding the eDRX bottom current of the 9160 module:

1. They observed individual variations across different SiPs, with some samples showing a bottom current that is approximately 2 µA higher than others.

2. They also noticed that the bottom current increases as the temperature rises. While I understand that this is typical behavior for semiconductor devices, they would like to know if we have more precise data or characterization results to share on this temperature dependency.
   

Best regards,

Jayant

[Simon D-M]

Hi Jayant,

They observed individual variations across different SiPs, with some samples showing a bottom current that is approximately 2 µA higher than others.

The nRF9160 consumption is less than 10uA when idleing in eDRX (6uA -> LTE-M, 9uA -> NB-IoT). You can find the documentation about it here.

They are seeing this 2uA deviation, but what is the actual floor current? To evaluate whether this 2uA is a lot or not, the context is really important here.

This deviation has plenty of possible sources. Without more context, the most plausible cause may be the SIM card. Please check if your SIM card supports supply shutdown or if it has a low-power mode for eDRX. Also you can try to switch the SIMs between 2 devices that show a high deviation and see if the extra consumption has switched boards.

They also noticed that the bottom current increases as the temperature rises. While I understand that this is typical behavior for semiconductor devices, they would like to know if we have more precise data or characterization results to share on this temperature dependency.

Here are some temperature characterizations. These are not focused on eDRX floor current but with a bit of extrapolation you can see what to expect from a change in temperature.

And again, most likely the biggest consumption here is not the nRF9160 itself, but probably the SIM. So maybe the difference is caused by the SIM and not the nRF9160.

Best regards,

Simon

[Jayant Tang]

Hi Simon,

Thanks for your reply. The bottom current of these two 9160 SiPs are 6uA and 8uA.

I‘ll ask them to exchange the SIM card and test again.

Best regards,

Jayant

[Jayant Tang]

By the way, they're using the latest mfw_1.3.8, in which it will disable the SIM during eDRX.

[Simon D-M]

Hi Jayant,

Jayant Tang said:

Thanks for your reply. The bottom current of these two 9160 SiPs are 6uA and 8uA.

Yeah, in this context, 2uA is quite a lot. I don't think the SIM cards are to blame here. If the SIM was sleeping, I would have expected tens of uA.

I couldn't find any tolerence range for the nRF9160 in the documentation. I'll try to see internally if anyone knows anything about it and I'll get back to you.

In the meantime, can you maybe share the hardware file so that I can quickly check if there is something else in the hardware that could cause this difference...

Best regards,

Simon