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Thread: Teensy 4.0 USB host current limit chip

  1. #1
    Junior Member ghostintranslation's Avatar
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    Teensy 4.0 USB host current limit chip

    Hi,

    I'm making a board for Teensy 4.0 that will use its USB host capability. I read somewhere in the forum that Teensy 4.0 does not include a USB current protecting chip and that it is required to prevent burning it. I read that the chip to use would be the TPD3S014.

    Is there any similar chip but with a through hole package instead of SMD?
    I don't have the tools nor the experience that's why I'm looking for that. I tried searching on the Texas Instrument site and on Digikey site but without success.

    Thanks

  2. #2
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    Quote Originally Posted by ghostintranslation View Post
    Hi,

    I'm making a board for Teensy 4.0 that will use its USB host capability. I read somewhere in the forum that Teensy 4.0 does not include a USB current protecting chip and that it is required to prevent burning it. I read that the chip to use would be the TPD3S014.

    Is there any similar chip but with a through hole package instead of SMD?
    I don't have the tools nor the experience that's why I'm looking for that. I tried searching on the Texas Instrument site and on Digikey site but without success.

    Thanks
    i have had good luck in the past using "surf boards" that i get from digikey. i usually trim them to remove UN-needed space.
    use very small tip 20 watt iron, pre-tin the board and the part legs, and tack just one pin to get started which may take
    more than one try but once you have good position and one leg tacked, it is very easy after that. smallest pin spacing
    i have done so far is 1.27 mm

  3. #3
    Senior Member+ defragster's Avatar
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    There are larger SMD parts - loglow/TallDog board is moving to this that others may use : TPS2055A - not sure if that is larger than TPD3S014. The first beta board was a tiny part that soldered okay here.

  4. #4
    Junior Member ghostintranslation's Avatar
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    Thanks for the answers,

    According to the datasheets of these 2 chips, the TPS2055A is bigger yes, still SMD though but it seems to not exist in through hole package...

    Thanks

  5. #5
    Senior Member PaulStoffregen's Avatar
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    Quote Originally Posted by ghostintranslation View Post
    and that it is required to prevent burning it.
    The current limit chip is meant to be used together with a large (100 uF or more) capacitor. Together they serve these functions.

    1: If the USB device or cable has a failure, the current is limited.

    2: When you hot plug a USB device, a large surge of current is needed to rapidly charge its capacitors. The 100+ uF capacitor provides most of this current. The current limit chip prevents too much of the current from being taken from the capacitors that are keeping Teensy running. Sometimes this isn't an issue, like when Teensy is powered by a strong external power supply.

    3: When Teensy is powered only by USB, the current limit chip prevents that large capacitor from charging too rapidly from the limited current available over the USB cable. Your PC or Mac or USB hub may have limit current limit chips & capacitors.

    If you leave everything plugged in, and your power source provides protection in case of a short, you may not need the current limit chip. Its main purpose is to support hot plugging the USB device while power is on.

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    Junior Member ghostintranslation's Avatar
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    Thanks for the detailed response.
    I'm not going to take any chance to forget to unpower the Teensy before unplugging the USB so it's not optional to me.
    I saw on the schematics of the chip that they use 2 capacitors, one of 0.1uf and one of 22 uf, do you think it's better to use just 1 100uf instead?

  7. #7
    Junior Member ghostintranslation's Avatar
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    To be more precise I am referring to this schematics:
    Click image for larger version. 

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    so 2 capacitors on the out: 0.1uf and 22uf
    You would replace those 2 by 1 of 100uf?

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    @ghostintranslation - don't be afraid of SMD. All you need is reading glasses and an iron with a small tip.
    This is what I did to test op amp, with a chip similar to the limiter you need: Click image for larger version. 

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    Also, there is a bunch of videos on YouTube about dealing with SMD's with a simple iron. Just try it, you'll see how easy it is.

    For the setup, look here, just a few lines below this post: https://forum.pjrc.com/threads/57975...using-USB-host
    It worded fine for me. I connected this to Teensy and it I was getting all the good MIDI events. Just plugged it in, no brownouts.
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

  9. #9
    Senior Member+ KurtE's Avatar
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    As for setup of the TPS... There are several postings on the monster thread (T4 first beta)
    There is some information from @mjs513 that was updated by @Paul in the postings starting about: https://forum.pjrc.com/threads/54711...l=1#post200756

    SMT soldering - I am still not the greatest at this, so typically I try to keep components at least the size of 0805. The larger chip for USB is not too bad to solder. I simply use a smaller tip on my soldering station, plus water washable flux (and solder) and I have a lighted magnification lamp on my desk that I look through as I solder...

  10. #10
    Junior Member ghostintranslation's Avatar
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    Thanks for the advices, I guess I'll have to give it a try...

    Thanks also for the schematics, it's different than the schematics from TI but I will trust what was tried here.

  11. #11
    Senior Member PaulStoffregen's Avatar
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    Yes, use larger capacitors. TI's suggestion is not enough to support reliable hot plugging in this case.

    The output should be 100 to 220 uF. USB spec says 120 uF minimum. Aluminum electrolytic, tantalum or ceramic are ok. But avoid low quality ceramics... the ones which start with Y or Z, like Y5V or Z5U. Physical distance between the chip and capacitor and connector is not critical.

    The input should be 1 to 10 uF. Best to use ceramic. The input capacitor should be located close to the TPS2055A.

  12. #12
    Junior Member ghostintranslation's Avatar
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    Ah, thanks for these informations, I'll make the changes

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