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+2.5V external regulator powering to HDMI_VPH

diegopm , 12-13-2018, 11:21 AM
Hi Experts,

Openrex design has HDMI_VPH, NVCC_LVDS2P5, NVCC_MIPI, NVCC_RGMII, SATA_VPH and NVCC_ENET connected to external 2,5V regulator. I have the same schema in my imx6solo design, I have HDMI_VPH, NVCC_LVDS2P5, NVCC_MIPI, NVCC_RGMII and NVCC_ENET connected to an external regulator. I also saw this schema in an evaluation board of Freescale, but this was as an option with 0ohm resistor.

In production, a few boards have an issue with HDMI_VPH (ball M7). The boards run properly initial tests but fails in the next steps of production. Under failure, +2V5 rail is tied to GND due to internal short-circuit into M7 ball of imx6solo. If I remove power from M7 ball, the +2V5 rail is up again and board runs properly, except HDMI because HDMI_VPH is internally short-circuited to GND and not powered.

IMX documentation connect HDMI_VPH, NVCC_LVDS2P5, NVCC_MIPI to VDDHIGH_CAP (internal LDO output).

I would like to know if Openrex project had a similar issue, and how you solved it.

robertferanec , 12-17-2018, 02:30 AM
Hi @diegopm, I have not seen any issue like this on none of our iMX6 boards.

Does HDMI on your board uses ESD protection? Looks like HDMI block may be damaged for some reason (could be also over voltage on 2.5, but then other chips connected to 2.5 would be probably damaged too).
diegopm , 01-04-2019, 04:07 AM
Hi Robert, thanks for your answer.

My HDMI port is protected by CM2020 chip.

I am thinking ESD problem could be possible at manufacturing time, due to manipulation of the board. But I am under investigation to discover the cause of this issue.
For now, I cannot discard a design issue, in the power up sequence for instance. So, I would like to share a diagram and my powerup sequence, if something could be wrong at a glance, let me know.

Thanks so much.
robertferanec , 01-07-2019, 05:03 AM
Just a weird question - are all the processors same? I am not sure, but maybe some Solo CPUs may not have support for HDMI? I believe, that is probably not the problem, but who knows, it's just and idea to double check the part numbers on the processors.
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