ESD protection on a USB port - Page 1
Forum section: electronics / beginners

author: ultrageek.lloyd
author_rank: Contributor
timestamp: August 28, 2012, 04:05:32 pm
content: Hi,I'm currently laying out a board with a couple USB ports on it, and I want to know what kind of input protection I need on them. I've never dealt with input protection before, so I don't really know where to start looking. I've found the mouser ESD suppressor category, but that has parameters like breakdown voltage which I have no clue about. As input protection isn't officially a part of the USB spec, I'm not really sure which direction to go. Any help would be appreciated.Thanks,ultrageek

author: AndyC_772
author_rank: Super Contributor
timestamp: August 28, 2012, 06:12:35 pm
content: Google really is your friend here, just look up "USB ESD protection" or similar. There's loads of parts and application notes out there on the subject.Here's one:http://www.digikey.com/Web%20Export/Supplier%20Content/Wurth_732/PDF/Wurth_The_Protection_of_USB_20_Applications.pdf?redirected=1

author: dfnr2
author_rank: Regular Contributor
timestamp: August 28, 2012, 10:56:32 pm
content: Those application notes are great. However, be aware that such notes are not, in isolation, an adequate prescription for ESD protection, or EMC compliance in general. They need to be taken within the context of the overall EMC plan. Without an overall cohesive approach to EMC designed in at that start, your device will fail. Once you have your framework, then you can worry about each port.Start with the basics (constraints on the enclosure, board size, board shape, connectors). Come up with your basic stackup and ground scheme, organize your connectors, then add appropriate ESD/EMI/suppression protection on each I/O or connector.I thinkHenry Ott's bookis a great all-in-one reference and guide for EMC. This is a sort of EMC bible, but is full of practical wisdom and advice, and is very readable. There are a few good websites for EMC resources. TryKeith Armstrong's site; he also published some books that I have not reviewed, but look interesting. Also,Doug Smith's websiteis a great reference just for learning by exploration.There were a couple of good threads on this board with some examples, with respect to ESD planning, although that may be one part of the overall design. Check out:https://www.eevblog.com/forum/microcontrollers/robust-microcontroller-input-protection/https://www.eevblog.com/forum/projects-designs-and-technical-stuff/input-protection-questionGood luck!

author: free_electron
author_rank: Super Contributor
timestamp: August 28, 2012, 11:08:57 pm
content: usb6b diodes. sot23 package. simply route usb signals through them

author: hlavac
author_rank: Frequent Contributor
timestamp: August 29, 2012, 12:11:43 am
content: I've usedUSBLC6-2SC6.Protects both power and data lines, and is fast enough even for USB 2.0.Not too expensive either considering you can protect whole USB port with just one device.Bought mine atFarnell.

author: ultrageek.lloyd
author_rank: Contributor
timestamp: August 29, 2012, 05:15:16 pm
content: Thank you all for your replies. It looks like I will need to do a little bit of research on this before I finalize the design. dfnr2, thank you for those links. I will definitely take a look at those as I plan out a solution.Cheers,ultrageek

author: Christe4nM
author_rank: Unknown
timestamp: August 29, 2012, 07:54:34 pm
content: Hi Ultrageek,Maybe thisapplication noteby NXP might help tooAlso be shure to taketheir ESD protection devicesinto consideration, since they are quite cheap (example atFarnell), yet very good quality.Good luck!