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Thread: Teensy 3.6 external power via VIN and the GND near pin 13 ?

  1. #1

    Teensy 3.6 external power via VIN and the GND near pin 13 ?

    I am designing a PCB for a robot. It has a socket for a Teensy 3.6, which will act as the robot's microcontroller. Is it OK to power the Teensy by connecting 5V to the Teensy's VIN pin and ground to the Teensy's GND pin next to pin 13? My assumption is that all the GND pins are connected to each other so that would be OK. Or do I need to use the GND next to the 0 pin?

    Also, do I need to cut any leads on the back on the Teensy when providing external power like this?

    The reason I'm asking is because I smoked my Teensy, so I'm trying to figure out why. I just wanted to confirm that my initial assumptions were valid.

  2. #2
    Senior Member
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    You can supply a Teensy via Vin, and the onboard reg will step it down to 3.3V as long as you watch the 6V max in your power supply design. Any of the ground pins will work, though running other supplies through the gnd pins (say a stepper driver from near pin 13 to the gnd on the USB jack end) of the board can cause noise problems if they are noise.

    You can run into trouble if you supply USB power while also powering via Vin since the two power supplies can end up cross feeding each other. This normally is just a problem for the supplies, for example feeding 5V into your PC and causing trouble there not on the teensy itself. So normal solution is the cut the trace between 5V USB and Vin but other options exist.

  3. #3
    Senior Member PaulStoffregen's Avatar
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    All of layer 2 inside the PCB (6 layers total) is a ground plane, so any of the GND pins should be fine

  4. #4
    OK. Thank you. My approach should be OK then.

    I checked all the pins in the socket with a multimeter. I found my problem. I had a stray lead connecting 12v to the TX1 and another stray lead connecting 7.4V to the A2 line. When I turned on power to the PCB, it burned a 1/2" hole in the Teensy 3.6's main chip in about 1 second. Now that I found the issue in the PCB design, it's super easy to fix the PCB (cut the leads), revise the design, and replace the Teensy. I'm very glad it turned out to be something so simple and easy to understand. (I worried that it was going to be some complex mysterious electrical problem that I could not figure out).

  5. #5
    Senior Member PaulStoffregen's Avatar
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    Yup, 12V will destroy a Teensy. So will 7.4V. Either GND is.

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