iMX8MP - Typical Expected Power Consumption

[cushychicken]

What's typical expected power draw of the iMX8MP SOM with the buildroot-imx image running on it?

I seem to recall it being around 4[W] booted to the Linux command line, with a spike up to 6[W] during the initial Uboot/kernel startup phase.

Asking because I think I may have damaged my board - it's drawing closer to 12[W] on bootup now, and the PMIC is getting quite hot after running for a minute or two. The board will eventually power cycle itself and get trapped in a boot loop - I believe due to the PMIC going into thermal shutdown. I say "believe" because I have observed the PMIC triggering the POR line into the SOC when these power cycles / boot loops happen using my scope, but I haven't been able to instrument the I2C bus in order to check the PMIC's fault status register.

I suspect I may have damaged the SOM one of three ways:
- an ESD strike (it has been very low humidity here as winter comes on),
- I damaged the SOM when removing it from the base board the other day,
- trying to run the freescale_imx8mpevk_defconfig image from buildroot - though I think there is a low chance of this causing this type of error, as the DTS files don't seem very different. (I tried compiling an image with the latest stable version of buildroot just to see if the board would boot - and it did with release version 2024.08)

One last note: when running the 2024.08 image built with the freescale_imx8mpevk_defconfig image, I did manage to see some dmesg traces when running the newer kernel indicating PMIC interrupts for die temperature exceeding 105 deg C, then 125 deg C, which gives me more circumstantial evidence that PMIC overheating is the source of the boot loops.

(The fundamental cause of the big uptick in PMIC power consumption, I still don't know.)

I have ordered replacement SOMs and EVKs, but I would appreciate some input on this from Olimex as I wait for my replacement hardware to ship. It would at least help me confirm that this behavior is not normal.

Thank you!

[LubOlimex]

There is definitely something wrong, 12W is too high of power draw. Expected draw is up to around 1A at 5V (5W).

Is this 12W for the EVB board? Maybe track the schematic of the EVB starting from the power jack and check components of way of power. Maybe D3 SMBJ6.0A got damaged or some of the components after it.

[cushychicken]

Yes, 12[W] is for the SOM + EVB together.

I disassembled the SOM from the EVB, and the EVB alone draws next to nothing - about 5 mA - so I don't believe it's a diode problem.

The PMIC, however, quickly becomes too hot to touch - even from the back side of the PCB.

I'd love a confirmation of SOM + EVB power draw when running the buildroot-imx image, if that is something you are capable of supporting. Peak power draw at boot and also power draw when idle at the command line would be fabulous.

Any input on potential support of the freescale_imx8mpevk_defconfig? I looked at it a second time this morning, and I am not seeing anything that is a significant or potentially destructive deviation from the Olimex board's dts file. Mostly hoping that I can rule that out as a potential source of this problem.

Thank you for your quick response!

[LubOlimex]

> I disassembled the SOM from the EVB, and the EVB alone draws next to nothing - about 5 mA - so I don't believe it's a diode problem.

Hmmm, well there is nothing to draw current if there is no SOM on top of it... Did you place another SOM on top of the EVB?

Without having another SOM or/and EVB it would be hard to determine whether the problem is on the SOM or EVB part.

But if the problem is on the SOM it would be hard to repair.

> Any input on potential support of the freescale_imx8mpevk_defconfig?

I don't understand this question or request. We add own imx8mp-olimex.dts via patch and defconfig and you can compare with what you use with the files form this commit:

https://github.com/OLIMEX/buildroot-imx/commit/fcf7064d442075c204168eaff8e92883ed7bf9e8

[cushychicken]

Hmmm, well there is nothing to draw current if there is no SOM on top of it... Did you place another SOM on top of the EVB?

Well, you originally suggested a potential problem with D3 on the EVK carrier board (SMBJ6.0A). I suspected a similar problem, so I disassembled the SOM from the from the EVK, and powered up the EVK by itself, to see if it drew any serious current. (I have worked with that SMBJ series of Zeners before and have seen them fail short.)

That did not draw any current, so I was able to rule out the EVK as the source of the problem.

Did you place another SOM on top of the EVB?

I have not yet. I have ordered two replacements for each, but they have yet to arrive.

I don't understand this question or request. We add own imx8mp-olimex.dts via patch and defconfig and you can compare with what you use with the files form this commit:

Sorry, poorly phrased question on my part. A more accurate question would be: how could I migrate this dts and defconfig to a newer version of buildroot?

I think it'd be a matter of moving the patch file and defconfigs into the proper directories in the newer buildroot version, and then configuring the toolchain to search for them.

[LubOlimex]

Yes, you can try that. Just look at the commit I linked in previous comment and to the same for the newer sources. The changes from that commit are all we've done to add olimex support (nothing extra).