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high speed traces and solving impedance control ....
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luudee:
Guys,
I have a bit of a design challenge:
I have a USB 3.2 controller, on a custom PCB I am designing
for a customer.
The customer has requested that both a USB-A and a USB-C
connector be connected to that single controller, such
that the customer may choose which interface to use.
Now, this sounds simple enough, until you look at the signals.
The RX/TX lines for USB 3.2 are point to point, 90 ohm
terminated lanes.
I must admit, I am not a RF/high-speed PCB layout person.
Is there a way to make this work? Placing the connectors
and their pins close together (on opposite sides of the PCB),
and just do the best possible impedance matching?
I am at loss, any ideas/suggestions?
Cheers,
luudee
nctnico:
You can only achieve this by adding zero Ohm 0402 strapping resistors (or capacitors if you need capacitive coupling) that select which connector to route the signal to. A clever trick is to overlap the pads so the impact on the transmission lines is minimal. A good way for the signals to arrive at the strapping resistors is from a different layer. But there can only be 1 connector placed at the time. You can't have both. If there needs to be an option, then supply a USB-C to USB-A adapter with the product.
If the interface is a host, then you can opt to put a USB-C hub chip on the board to create multiple ports.
Someone:
--- Quote from: luudee on August 16, 2023, 04:04:54 pm ---The customer has requested that both a USB-A and a USB-C connector be connected to that single controller, such that the customer may choose which interface to use.
--- End quote ---
Sounds like a hub /s
langwadt:
--- Quote from: Someone on August 16, 2023, 11:10:25 pm ---
--- Quote from: luudee on August 16, 2023, 04:04:54 pm ---The customer has requested that both a USB-A and a USB-C connector be connected to that single controller, such that the customer may choose which interface to use.
--- End quote ---
Sounds like a hub /s
--- End quote ---
without a hub it's only a matter of time before someone complains that they can't use both at the same time
luudee:
--- Quote from: langwadt on August 16, 2023, 11:14:32 pm ---
without a hub it's only a matter of time before someone complains that they can't use both at the same time
--- End quote ---
We don't need a hub, it will be an either or solution.
Has anybody used something like HD3SS6126 ? I'ts a USB 3 mux. But now I will need some
logic to detect which connector is used ....
May be a current sense to control the mux ?!
Thanks,
luudee
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