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Original question:

TMS320F280049C: XDS110 disconnects due to switching noise

TMS320F280049C: XDS110 disconnects when PWM given to motor

Amar Hinduja
Prodigy 70 points
Part Number: TMS320F280049C
Other Parts Discussed in Thread: LAUNCHXL-F280049C, LAUNCHXL-F280039C

Hello,

Isolated cjtag debugger on board the LAUNCHXL-F280049C works properly with an inverter till the motor is not connected.

When motor is connected and PWM applied, connection breaks. However, motor keeps running.

I suppose, only the cjtag connection breaks.

Inverter dc link : 600V

The power stage of the inverter is EMC compliant. Only the control board is new and connected via cjtag to launchxl isolated debugger.

There are other posts too , mentioning this problem.

Before we start the EMC excercise, I was wondering whether you or any user could provide some hints for a solution to the problem.

I think you should prepare an application note for this problem , as most users would encounter this problem at some point or the other.

Regards.

AAH

  • 0
    TI__Guru 50611 points

    Hi Amar,

    The subject matter expert for Launchpad is out of office today. He will be back in office on Monday. Please expect response by Monday.

    Thanks & Regards,

    Santosh

  • 0 in reply to Santosh Jha
    TI__Mastermind 45606 points

    Hi Amar,

    Are you using the LAUNCHXL-F280049C just as an isolated debugger to another controller board? i.e. not using the F28004x on the LaunchPad itself.

    Amar Hinduja said:
    Inverter dc link : 600V

    The isolation strength between the XDS110 debugger and F28004x target side of the LaunchPad PCB is not rated this high (assuming the F28004x target side is on the HOT inverter side of the system). I'm not surprised the CJTAG connection breaks as the LaunnchPad is not intended for high voltage applications.

    Amar Hinduja said:
    Before we start the EMC excercise, I was wondering whether you or any user could provide some hints for a solution to the problem.

    Few suggestions below:

    • Try standard 4-pin JTAG instead of 2-pin CJTAG, if possible (CJTAG is bi-directorial in nature, which can be more susceptible to noise)
      • Slow down the JTAG speed in CCS settings as well
    • Suggest looking into using some other debugger solution with better isolation strength. Blackhawk has some options I believe (https://www.blackhawk-dsp.com/products/jtag-isolation).
      • Also the isolation strength on LAUNCHXL-F280039C has been increased over LAUNCHXL-F280049C. Used ~100mil vs ~25mil isolation barrier on the PCB. I can't guarantee it will work for your system however.
    • Can try adding a ferrite bead onto the USB cable going to your PC for added filtering

    Best,

    Kevin