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Thread: Help with VUSB and VIN

  1. #1
    Junior Member
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    Help with VUSB and VIN

    Hello all! I have designed a board at the teensy 3.6 will sit on that will have been built in 5 volt regulator. have read about cutting the trace between VUSB and VIN. Is this only a problem when programming the teensy? Is it possible to just be careful and avoid this issue? I have also read about removing the power from your USB cable. What is the best solution?

  2. #2
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    What is the best solution?
    TPS2113A Power Multiplexer Carrier with USB Micro-B Connector, Status: Active and Preferred
    or
    FPF1320 Power Multiplexer Carrier with USB Micro-B Connector, Status: Not Recommended for New Design.

  3. #3
    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by xman4242 View Post
    Hello all! I have designed a board at the teensy 3.6 will sit on that will have been built in 5 volt regulator. have read about cutting the trace between VUSB and VIN. Is this only a problem when programming the teensy? Is it possible to just be careful and avoid this issue? I have also read about removing the power from your USB cable. What is the best solution?
    It really depends on several things.

    If you are always willing to plug in your regulator, even when programming, then just cut the VUSB->VIN solder joint.

    If you want the option to run off of USB, a non-automatic solution is to just use a on-on switch. After cutting the VUSB->VIN solder joint, connect your regulator's 5v pin to one side, connect VUSB to the other side, and connect the middle pin to VIN. So if you don't have USB connected, you can use the switch as an off switch.


    A really simple solution is just to attach a jumper wire to VUSB, and only connect it to VIN when you need USB power.

    An automatic solution like the Pololu board posted would work. For the prototype boards I typically setup, that board is usually a little too large. Since it also has a USB connector, if you use that connector, you would need to fashion a USB cable (or solder the D-/D+ pads on your teensy to that board), but since the Teensy already has a USB connector, it may not be worth it to use the USB connector in that board.

    If you are designing a PCB, and will have other parts soldered on to the board, you could consider just buying the TPS2113APWR chip, and building your own circuit:


    Or you can just fashion a USB cable that doesn't have a power line. The trouble with that solution is sooner or later, you will use a normal USB cable, and not the special cable.

    I could imagine setting up some diodes so that the regulator's power isn't used if USB power is available.

  4. #4
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    Thank you both for your responses! I will look into some solutions that I can build into my board. I suppose simple caution is always an option as well.

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