nRF9151 LACA A0 revision PSM current increase compared to A1 revision

[Reinis0]

We have a device that is using nRF9151 for LTE-M and GPS. The device has 2 versions, one with U.FL and other with chip antenna with matching network.

During testing we found that the device with chip antenna had higher PSM current than U.FL version. U.FL version PSM was 8-9uA (with other ICs on the PCB) and the chip antenna PSM current was changing from device to device in range of 18uA to 80uA (also other ICs on the PCB, but determined that the difference was made by nRF9151 no other ICs).

Later we noticed that the chip antenna device was using nRF9151 LACA A0 hardware revision and U.FL was using A1.

From one of the chip antenna devices we removed the nRF9151 A0 and soldered on nRF9151 A1 form U.FL devices.
This caused the PSM current to drop from 75.8uA to 8.8uA. There are images from our testing bellow.
And if the device does not make a LTE-M connection, but goes straight to PSM the currents are the same for A0 and A1 revisions, suggesting that its a RF issue.

Current consumption using the device with nRF9151 A0.

The same device but with A0 removed and A1 revision soldered in place.

In short the A0 revision has a higher and more unstable PSM current than the A1 revision.
Didn't find this issue described in the A0 errata or that its fixed in the A1 errata.
Is this a know issue and is there a FW fix for this?


Thank you for help with this!

[Achim Kraus]

NCS 3.2.4, mfw 2.0.4, using two nRF9151-DK, one with A0A and one with A1A I get in both cases 3.4µA. At least on my side it seems, that there is no general difference in the quiescent current.

Maybe other source or a specific setup causes your difference. Do you use some COEX or other antenna tunning functions?

80µA is a value I remember from the Thingy:91X with enabled BLE. There it was caused from an antenna switch. 

[Reinis0]

COEX0 is used only to turn on GPS LNA on both devices, but only the chip antenna board has a LTE-M matching network.
It would be weird if it was something else, since I used the same board, the same components, same modem FW and same application and after resoldering A1A in place of A0A the current significantly decreased.

[Achim Kraus]

Reinis0 said:

It would be weird if it was something else

According your tests, maybe. But I guess, it will be very hard for others to reproduce your result.

According my test with two DKs, it MUST be something else as a general issue with A0A and A1A. And I guess, it will be easy to reproduce for others.

So, maybe you try to strip your app to run on a DK and we will see, if your result is reproducable.

[Achim Kraus]

I used now also two Thingy:91X, again one with a A0A and one with a A1A. And in both cases I get 8.5µA (measured at the battery plug as overall quiescent current).

Though you have different results, I assume it must be something special on your side.

(I would also test with Jared's nRF9151-feather , but all my A0A devices are in the field and I guess it will take one or two years for those devices to get back into my lab ;-) ).