USB Shield. To ground or not to ground? Asked 5 years, 5 months ago Modified 6 months ago Viewed 35k times 46 I have been given a device at work to do some testing on. Basically an IC is becoming obsolete so I need to test a replacement part. Upon redoing the ESD checks, the device failed. #1 I have been trying to understand how to ideally handle the cable shield on a USB device. (Full Speed USB, in this particular instance.) As seems to be the case with many signal integrity issues, contradictory recommendations abound, each with its own unsupported claims. Even authoritative-sounding sources such as Texas Instruments,
Electronic arduino How to correctly connect a USB shield on a PCB Valuable Tech Notes
The only real drawback to a direct shield to GND connection is that you wouldn't get any filtering of ground plane noise on cables, which could lead to EMI issues or potential ground loop issues, but I would think because USB cables are so short, ground loops aren't really much of an issue. 1 The shielding on a cable is to avoid interference from the outside world however it is always tied directly to the GND pin. Not inside the cable itself but inside a device. Every single device I take a look at, will do this, computer/hubs, usb soundcards, usb bluetooth dongles, usb powerbanks, usb harddrives, arduino's etc. 1 @tobalt USB cables are certainly not always shielded. About a third of all cables I tested were not shielded. Users must use a USB cable, but I can't guarantee they will use shielded ones. And even if all USB cables were shielded, I still don't know if the user's motherboard has tied shield to GND on the host end. Aug 10, 2023 at 6:38 1 Answer In most applications, the USB shield should not be connected to ground (GND). The shield only needs to be connected on one side of the cable, and the USB host side will normally be connected. The shield should still be soldered, however, for physical stability. Title USB Shield Recommendations URL Name usb-shield-recommendations Interface
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The USB shield is connected to system ground via a 120R@100MHz ferrite bead. The board has a power prioritization scheme going on, so it can be either bus powered, powered via a power supply or from a battery. I tested the prioritization circuit extensively, and the priorities and the make-before-break behaviour work just fine. 16 I have a PCB with a few USB and RJ-45 Ethernet connectors on one side. I'm quite confused as to how exactly I'm supposed to be hooking up the SHIELD pins on them though. This is for a host device that will interface with peripherals. It is provided regulated 5V 10A power by an external PSU, and is intended to be used inside a vehicle. There's lots of USB devices, and how they connect the shield/cable ground to the system ground inside the devices depends on the manufacturer. If the device is plugged in, the cable/shield ground is connected to the chassis ground of your computer and is as grounded as it is. If the device isn't plugged into anything, you should be able to toss. According to the recent USB Type-C specification, Standard-A to Type-C cables must tie GND+Shield together within each plug so that the shield braid can carry some of the return current. It can also help control electro-magnetic interference (EMI) by ensuring the shield braid is well grounded. Typically, the shell contact is not optimal on USB.
'Floating' ports can sink the ship USB shield grounding \ VOGONS
1 Like LarryD February 16, 2022, 7:18pm 2 521×550 2.55 KB GND on most computers is connected to earth. A shield is connected to earth on one end of the cable. Burakimportant February 16, 2022, 7:31pm 3 Thanks for the answer, Correct me if I am wrong. Most computers shield is connected to gnd. So I don't have to ground the shield again. Right? Re: USB ground, USB shield ground, analog ground, power ground; grounding. FWIW, in Teensy 2.0 and SparkFun Pro Micro boards (both ATmega32u4), there is a single ground plane. The USB ground and shield are connected to the ground plane at the connector. Both of these boards have pretty good ADC performance, in my opinion.
Should the USB shield on the USB connector be connected to ground (GND)? Most applications should avoid using the USB shield to ground (GND). On the USB host side, the shield can only be connected to one side of the cable at a time. USB-C is quickly becoming the de facto connector for high-speed data transfers. Shall we connect the shield of a cable to signal GND or Earth GND? Answered by Rick HartleyWatch the full interview here:- Ground in PCB Layout - Separate or.
'Floating' ports can sink the ship USB shield grounding \ VOGONS
USB has high-frequency signals that need the shield to be grounded at both ends. "EMI and USB". Intel says to connect the shield (connector shell) directly the the ground plane, and optionally use a ferrite bead between the USB GND wire and the ground plane. "Intel EMI Design Guidelines for USB Components" p. 9. According to USB 2.0 standard, a USB cable must be made minimally of 5 conductors: the two power supply wires, the differential pair for communication, and a fifth conductor for shielding made of a stranded copper bread, which must surround all the others on the whole length of the cable and be connected to the plug shells at both ends.
