Author Topic: Unpowered USB esd protection  (Read 689 times)

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Offline zittTopic starter

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Unpowered USB esd protection
« on: August 22, 2019, 03:17:11 am »
My computer desk is a mess... I'm always loosing USB memory sticks because I don't really have a way to storing them. They tend to migrate everywhere.. multiply... get lost... fall to the floor - get kicked under the desk... repeat... rinse. You get the idea.

I want to make a perm home for these little buggers so:
1) I can easily find them.
2) organize them
3) store them

But I don't want to just throw them in a drawer - because drawers tend to collect other things.
YEARs ago; I designed my own computer case and stand out of square tubing:


I've decided I want to mount the USB stick in vertical USB-A connectors to a PCB made at OSHPark. IE have them mount just like they would be in a usb port. It would be attached used a 3DPrinted bracket at a 45degree angle to the front of the computer stand.

Now obviously; I can just mount the connector as is with no electrical connections... but where's the fun in that?

I'm thinking I want to at least connect the grounds of the USB ports to a ground point on the nickel plated stand. I obviously don't want to run power to the +5V line of the connector; but should I consider ESD protection diodes? What about on the D+/D- lines?

I'm specifically looking at TI's app note:
http://www.ti.com/lit/sg/sszb130c/sszb130c.pdf
on page 13 as a reference.

Obviously - anything I do is way over kill at this point; but was wondering what you guys thought about ESD protection? Do it? if so; why? if not; other than costs - why not?

Should I put a large-ish resistor from +V to ground to bleed off any charged caps in the devices?
 

Offline wraper

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Re: Unpowered USB esd protection
« Reply #1 on: August 22, 2019, 03:24:49 am »
Quote
I'm thinking I want to at least connect the grounds of the USB ports to a ground point on the nickel plated stand.
Worst idea you could come up with. Grounding them won't make things better, only worse because with it appears path for significant capacitance/ discharge current. Like discharge path from human holding USB stick, through it and to ground. Also data pins are recessed, so there is little reason to bother about them during storage. Plugging them into connectors will increase connector wear. And if you do so, either leave all pins floating or just connect all of them together (within single connector) but don't connect to anything else.
Quote
I'm thinking I want to at least connect the grounds of the USB ports to a ground point on the nickel plated stand. I obviously don't want to run power to the +5V line of the connector; but should I consider ESD protection diodes? What about on the D+/D- lines?
Why would you use diodes when there is no voltage/signal to pass?
« Last Edit: August 22, 2019, 03:30:08 am by wraper »
 


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