Timeline for USB 2.0 HS: Common-mode chokes on DP/DM
Current License: CC BY-SA 4.0
4 events
| when toggle format | what | by | license | comment | |
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| Jan 7, 2023 at 7:54 | comment | added | Tim Williams | On the upside, cable-sized ferrite beads saturate much less quickly than chips do: some amperes usually, at which point I'd be concerned about cable heating. (For a single turn through a bead of given aspect ratio and material, saturation current scales proportional to diameter.) More for low-mu or accidentally gapped (snap-on style, say?) types, of course. | |
| Jan 7, 2023 at 7:51 | comment | added | Tim Williams | @tobalt "Unwanted" -- by whom? I would say to them, it's unavoidable; embrace it, work around it as needed. (Like I said, shield can be bypassed at AC, solving the [DC/mains] ground loop concern.) As for GND, it's just another wire inside the cable, a transmission line like the others; only the shield/screen is the reference for them all. Using GND alone for return current puts its own TL impedance in series to the shield; a messy proposition. At least, unless cables are made different than I think -- I admit I haven't dissected one in a while. | |
| Jan 7, 2023 at 5:04 | comment | added | tobalt | Cable bead solves many problems. But it will be made useless if you draw supply current through the cable and return it elsewhere (e.g. a ground loop though various chassis).. So i don't see the need to suggest connecting USBGND to shield ?! (it ends up so anyway often). JK return current can and should be handled by USBGND. That it also uses the shield is an unwanted side effect IMO. | |
| Jan 7, 2023 at 1:29 | history | answered | Tim Williams | CC BY-SA 4.0 |