Nvidia Jetson AGX Xavier Series Design Manual page 155

USB SS CONNECTOR PART SELECTION: CHOOSE A BETTER USB SS PART
A USB SS connector has many metal fingers that are perfect in length for radiating in and
around the 2.4 GHz band and beyond. A USB SS connector should be selected to minimize
radiation from the USB SS part itself. Some recommendations are:
Connector fully enclosed by metal
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No slots in the connector walls, or if there are slots, the size is very small. Also, the
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number of slots should be minimal.
Connector has as many grounding legs as possible. More legs provide better grounding
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from the USB SS exterior to the PCB and the structure is less likely to radiate. Choose 4
legged connectors over 2 legged connectors and so on.
The quality of the external USB SS device used in the USB SS port will have impact on the
overall experience. If the external USB SS device used in the USB SS port is of poor quality, the
part itself will radiate and issues will continue. A plastic base USB SS device works inferior
compared to fully metalized USB SS devices.
GROUND THE USB SS PART SOLIDLY
The USB SS connector is grounded through "the grounding legs" previously mentioned. Care
must be taken to ensure the leg area is a very good RF ground. One way to do this is to
increase the number of ground vias placed in the "grounding leg" area.
IMPROVE THE ROUTING AND GROUNDING AROUND THE USB SS PART AREA
The routing and grounding around the USB SS connector part area must be handled carefully.
Since this area is very "hot," any traces running on the surface layer below the physical
connector part can pick up noise and transfer it to other areas or radiate the noise. These
traces need to be moved to an inner layer, and this area needs to be made a very good ground.
BURY THE USB SS LINES IN INNER LAYERS
The USB SS lines should be routed as impedance controlled differential pairs, with ground on
either side and on the layers above and below.
SHIELD THE USB SS CONNECTOR PART
The radiation from the USB SS connector part is very strong. Need to make a "shield" and put
on top of the USB SS connectors. The shield must touch the USB SS body in multiple points.
The shield track must have number of grounding vias so that any emitted noise from the USB
SS connector is swiftly grounded.
Jetson AGX Xavier Series Product
USB SS and Wireless Coexistence
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