IMX7 PVCC_ENET_CAP temperature problem

[rfet]

Hi NXP

We have a small amount of Boards with iMX7solo where the processor does not boot properly. We have found that on this boards PVCC_ENET_CAP only rises to ~0.5V instead of ~1.8V (as it is on good boards). But when we heat up this boards, LDO for PVCC_ENET_CAP starts to work normally and goes up to 1.8V. Then these boards work perfectly. 

NVCC_ENET1 is 3.3V 

How can this behaviour occur? Is there any internal on/off signal for this LDO or are there any problems known?

Thanks and best regards,
Raphael

[rfet]

Hi Weidong,

After further investigations, we realize that neither CPU-Faulty soldering nor PCB quality can be the problem. We connected PVCC_SAI_SD_CAP to PVCC_ENET_CAP which leads to all faulty boards working fine (normally PVCC_ENET_CAP is not connected to other signals).

That means to me:
1. NVCC_ENET1-PIN is connected and soldered correctly (otherwise our ENET signals would not work)
2. PVCC_ENET_CAP-PIN is connected and soldered correctly (otherwise connecting PVCC_SAI_SD_CAP would not have an influence)
3. Connected ENET-IO-PINs could not have an influence, because problem with 0.5V on PVCC_ENENT_CAP is also happening in/after reset state of the processor.

Do you have any other ideas as to what may be causing this behavior?

Regards,
Raphael

[weidong_sun]

Dear @rfet ,

On page 465 of reference manual, we can see the descriptions:

PVCC_GEN_NET LDO is on by default. So don't need to switch it on manually when booting board.

According to your description, a small amount of boards exist the issue, other boards can normally boot.

So my suggestions is :

Contact local distributor FAE or local NXP FAE to evaluate the current situations, helping you find root cause.

Thanks!

Regards,

weidong

[weidong_sun]

Dear @rfet ,

See below, pleaes!

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The situation has no relations to the internal signals of i.MX7S, from your descriptions, you should check the issue from 2 aspects:

1. CPU Faulty soldering

2. PCB quality inspection

Suggest you'd better do No.1 , very possible that it is the root cause.

=================================

Thanks!

Regards,

weidong