LAUNCHXL-F28069M: Short-circuited supply rails, unknown reason

Hello there,

I am sorry to hear that this is happening.
Were these boards brand new?
Did the failures occur when the same computer or USB port was used? How about a different USB socket or computer. If it looks like it is just one PC, try a good board in that same PC. If it doesn't matter which PC is connected, then I suspect some ESD damage might have occurred.

Can you try one additional thing for me? On both a "bad board" and "good board" do the following:
- Remove Jumpers JP1 and JP2 to isolate the Emulator from the Device.
- Configure S1 to 110 -> position 1 on, position 2 on, position 3 off.
- short JP7
- open JP6
- Supply +3.3V to J9, or any other 3.3V on the device side of the board with a bench power supply.

With the above configuration, you will isolate the JTAG and PC from the Device. You will be powering the MCU with a bench power supply (my board shows 197mA at 3.3V being consumed on the device side. I am able to monitor the Serial output on my PC. Please share the results of your test.

Regards,
Mark

Hello, Mark.

It doesn't matter which PC. I tried your setup, and the bench power supply tries to gives maximum current (something is shortcircuited). In our case, 3.3V and 1.1A (maximum of this source) are supplied, the microcontroller starts to become hotter and hotter...

Then, if the reason is some ESD damage, what would you suggest to avoid the problem in advance?

Thank you very much.

Kind regards,

Guillermo

Guillermo,

It is very difficult to tell you exactly what happened to cause the damage. Generally, following proper ESD safe handling protocols will help to prevent these sorts of failures, but is not always guaranteed. Please check out this self-training (https://www.esda.org/about-esd/esd-fundamentals/) on ESD Fundamentals.

I have a few more questions to see if this is more of a systematic issue or not. At this point we have not received any complaints of build quality issues?

- Are these new boards? If not, how long have you had them? Can you provide a date of purchase?

- Have these boards only recently started failing? i.e. were they working before?

Are you the lab professor? Unfortunately at this time we are unable to ship additional LAUNCHXL-F28069M LaunchPads into the EU. But are currently working to resolve this. However, we expect this to resume in the near future. 

Thanks,
Mark

Hello, Mark.

Thanks for the manual about ESD, it seems really helpful. Regarding your questions:

-These boards are new. They were bought on 3rd February this year, from Farnell (code: 2465066). Since that moment, they have been used and some of them started failing (after working properly during some time).

Yes, I am the professor. Don't worry, we are not in a hurry right now, but we will need to buy more units on September.

Thank you very much,
Guillermo