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LMD18201

Rick Franda
Prodigy 30 points
Other Parts Discussed in Thread: LMD18201

I'm controlling a 24VDC servo motor with a 3A max current draw, using an Arduino Mega with Atmel 2560 micro-p, with the intent to deliver a 5V 500Hz PWM signal source.  In actuality, the voltage is about 3.6VDC (weak Arduino board?).  The PWM is sourcing the LMD18201. When I put the servo motor onto the H-Bridge for the first time the chip got hot and my coworker said he saw a spark, which I didn't believe, but the motor does not run.  I'll be using a new 18201 today.  I'm using the connection diagram from the datasheet.  A scope on the Arduino board outputs shows the signal that I desire.  Is there something I should be aware of that I'm missing with this application?  Must the chip be mounted to a heat sink, even during development?  At this point in development, I won't be operating the chip for more than a couple of minutes as I test the function.

Thank you for your help.

  • 0
    TI__Expert 6660 points

    Hi Rick,

    It would be interesting to see exactly which pin is damaged on the LMD18201.
    Could you please ohm out each pin on the device from "Vs Power Supply" and "Power Ground"?
    Do this for both a new and damaged device to see if we can isolate the problem.

    It’s possible that reversing the motor caused an over-voltage condition on the internal MOSFETs.
    Try adding TVS protection diodes to the design to prevent this condition.

    You can always order free samples from www.ti.com/samples

    Please let me know how your continued testing & debug goes. Best regards, Keith

  • 0 in reply to Keith Keller
    Prodigy 30 points
    Thanks for your help Keith. I just ordered samples of the LMD18201 - I could only get the surface-mount type. I would prefer the TA11B pkg, since I'll be hand soldering the pins to the application. I'll get back to you with the results of the resistance testing.