If the USB device is powered thru the USB connector, you probably could get away with tying the shield to the circuit ground. But if the USB device has it's own supply, you definitely want resistance between the shield and circuit ground to prevent ground-loop currents, which cause noise problems. That's probably where the 33K resistance came up.
The shield facilitates ESD protection because it is always connected first when doing a hotplug. BUT !!! Just because you have a shield does not guarantee you wont have ESD problems; there are many other things you need to do. On Sunday, February 7, 2021 at 6:07:08 PM UTC-8 Bill Stanley wrote: > Not a lot of help but from the USB spec: > 6.8 USB Grounding > The shield must be terminated to the connector plug for completed > assemblies. The shield and chassis are > bonded together. The user selected grounding scheme for USB devices, and > cables must be consistent with > accepted industry practices and regulatory agency standards for safety and > EMI/ESD/RFI. > > So in other words, the shield will pass thru both connectors to the > "chassis" but the connection to any ground is left to the reader. > I usually put a 0402 footprint from chassis to system ground. I then > install a 600 ohm ferrite bead. If needed, it can be deleted or changes for > a resistor or cap. > > > > > > On Sunday, February 7, 2021 at 5:26:57 PM UTC-8 M1 wrote: > >> I don’t know, but thought I might point out that it appears you have the >> USB connector running in line along the circuit board. Maybe you meant to >> do that though. >> >> >> >> Michail Wilson >> >> 206-920-6312 <(206)%20920-6312> >> >> >> >> *From:* neoni...@googlegroups.com <neoni...@googlegroups.com> *On Behalf >> Of *newxito >> *Sent:* Sunday, February 7, 2021 4:54 PM >> *To:* neonixie-l <neoni...@googlegroups.com> >> *Subject:* [neonixie-l] USB connector shield >> >> >> >> I'm trying to make a CPU load indicator with 3 IN-12. This is my first >> project using USB power and data from a PC >> >> I'm not sure about the shield of the USB connector, Google is a little >> bit confusing about this point... >> >> Basically I found 3 different opinions: >> >> >> >> 1. Do not ground the shield >> >> 2. Ground the shield >> >> 3. Connect the shield to ground trough a 33k resistor >> >> >> >> Can somebody give me advise? >> >> -- >> You received this message because you are subscribed to the Google Groups >> "neonixie-l" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to neonixie-l+...@googlegroups.com. >> To view this discussion on the web, visit >> https://groups.google.com/d/msgid/neonixie-l/8acdfa93-38c3-4ae6-b218-b5b1073fbed8n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/8acdfa93-38c3-4ae6-b218-b5b1073fbed8n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/211c9582-d65d-4c82-abd8-3fbaa600eafcn%40googlegroups.com.
