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USB disconnects when power connected to converter board

David Yellin
Prodigy 115 points

We are testing a high voltage LED converter design using the Launchpad XL F28027.

We use the isolated usb-JTAG interface on the board with all jumpers removed.

The converter is connected to a PFC. For test purposes we use the PFC from an ATX power supply. The PFC is powered through an isolated variable transformer. We also tried without the isolated transformer.

With power connected and 350 volts peak voltage to the converter everything is fine, but as soon as we switch the PFC on the USB disconnects with the following error

C28xx: Error: (Error -150 @ 0x0) One of the FTDI driver functions used during configuration returned a invalid status or an error. (Emulation package 5.1.507.0)

As soon as we turn the PFC off the USB connects again.

It doesn't seem to make any difference if the PFC is connected to a different circuit, or even from a long distance away.

I'm not even sure if this is related to the Launchpad itself or if it's a strange grounding issue.

Any ideas?

  • 0
    Guru 192875 points

    Hi David,

    David Yellin said:

    I'm not even sure if this is related to the Launchpad itself or if it's a strange grounding issue.

    Any ideas?

    This is due to your circuit has a lot of ground noise/ radiated noise when you're at high power. You need to shield your launchpad or go for external XDS100v2/XDS200 for better connectivity at higher power. 

    Regards,

    Gautam

  • 0
    TI__Guru**** 171609 points

    Hi,

    What Gautam mentioned makes sense - usually JTAG disconnect issues when load is applied to a system are caused by voltage transients and noise.

    How is the Launchpad powered? Is it from the same ATX power supply you are using? In this case I would try to separate the two power supplies and see if the same effect persists. To further reduce transients, I would also try to use the isolation transformer on the Launchpad's power supply.

    If you still see this issue, the noise from the PFC may be influencing the host PC - I would then use the transformer to isolate its mains (or use a battery powered laptop).

    In any case, I have seen other developers report similar scenarios and usually this requires a thorough evaluation of the system under test. We here at the CCS forum may not be able to help much further than that, but you can always double-check your system interconnects with the experts in the device forum.

    Hope this helps,

    Rafael

  • 0 in reply to desouza
    Prodigy 115 points

    Hi,

    Thanks for the suggestions, we found that indeed it was an EMI problem. By attaching several ferrites to the USB cable we were able to make everything work again.

    Regards,

    David

  • 0 in reply to David Yellin
    Guru 192875 points

    David Yellin said:
    Thanks for the suggestions, we found that indeed it was an EMI problem. By attaching several ferrites to the USB cable we were able to make everything work again.

    Excellent! Indeed the best way to tackle this issue.

    Goodluck & Regards,

    Gautam