IMX6 Quad Startup Issue

[stevelandas]

I have had two boards where the IMX6 fails to start. We have about 30 prototype boards total. The two that failed have been working and starting up correctly for a few months. 

The startup signals (PWRON_ POR_B, etc...) seem to be working normally.

The 26MHz clock is present.

All power rails are good. 

On power up the processor appears dead and no DRAM clock is started.

Is it possible to determine why the processor failed? 

[igorpadykov]

Hi Steve

to narrow down problem one can try to extend POR up to 1sec.

or change both crystals (24MHz, 32.768KHz), to define if this is due to clock problems.

Change processor to new one (if this is soldering or ESD issue) and check voltages (power problem)

using i.MX6 System Development User’s Guide

http://cache.freescale.com/files/32bit/doc/user_guide/IMX6DQ6SDLHDG.pdf

Best regards
igor
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[stevelandas]

Hi igor,

Thanks for responding. I will do as your request.

As for the voltages, I double checked the processor voltages and one is out of range.

the PMIC is programmed to provide 1.375V for VDD_SOC but it measures approximately 1 volt.

When I apply power to the system the PMIC comes up nomally but shuts down after about 3 seconds and is hot to touch.

I would like to disconnect VDD_SOC from the PMIC to the IMX6 by removing a zero ohm jumper so VDD_SOC would be floating. I could then see if the PMIC comes up and stays up but will this cause any damage to the IMX6 ( assuming its not already damaged)?

Thanks,

Steve

[igorpadykov]

Hi Steve

powers should be applied in sequence defined by datasheet power-up

sequence. Removing VDD_SOC is not allowed.

http://cache.freescale.com/files/32bit/doc/data_sheet/IMX6DQCEC.pdf 

Best regards
igor

[stevelandas]

OK, just thought it might be a good troubleshooting step.

Have you seen this type of failure before, where VDD_SOC is loaded down by the processor?

[igorpadykov]

in general this may be cased by overheating.

Best regards
igor

[stevelandas]

Hi Igor,

If it were caused by overheating would it have to be active, i.e. while running? Or, could it be passive, say during reflow?

I should have the new crystals to try today,

Regards,

Steve

[stevelandas]

Hi igor,

On one board I replaced the processor and it did solve the problem. Is there any investigation that can be done on the failed part?

You mentioned this could be caused by overheating. I don't believe this board was subjected to any temperatures above ambient. Could this be a latent failure caused during the reflow process? I do have units that have been running in an ambient temperature of 40C for over a month with no issues. Processor core temperature at about 83C as measured by the internal temperature sensor.

I will have the oscillators changed on the 2nd board.

Regards,

Steve

[igorpadykov]

Hi Steve

I believe yes, this may be caused by reflow process or esd.

Investigation on the failed part (FA) can be done through nxp marketing office.

Best regards
igor

[stevelandas]

Hi Igor,

I believe I may have found the cause of the failures but wanted to confirm with you.

In the data sheet it says that VDD_SNVS_IN must come up first but it may be connected with VDD_HIGH_IN.

They are connected in my design but they are powered from the MMPF0100 VGEN6 output and this output comes up after the power rails for the cpu (VDDARM_IN and VDDSOC).

Can you confirm that this could a startup issue that could damage the i.MX6?

Thanks,

Steve

[igorpadykov]

Hi Steve

yes violating power-up sequence may cause startup issues.

Best regards
igor