| General > General Technical Chat |
| high speed traces and solving impedance control .... |
| (1/1) |
| 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 |
| Navigation |
| Message Index |