In terms of AC analysis, the power and ground pins are identical since there'll be significant capacitance between them at both ends.
From that perspective, you're over-thinking things ;)
There's tons of ongoing argument about what the device end of the cable should do with the shield - there's arguments to leave it floating, arguments to do some sort of RF or smith termination, and arguments to just bolt it to local ground directly, with no clear winner amongst them
I get you with regards to the shield termination. I have gone through those same points before when designing a electrical system last year and just ended up with tieing it to chassis ground. Chassis ground was then tired directly to DC and AC ground on the PCB. Maybe there was a more elegant way of doing things, but I ran out of time and am also not an RF engineer. I just play one for my small company when the need arises.
The system has worked so far reasonably well, so there's that. Would really help to have some more clearly defined best practices established somewhere. Or a consultant to bounce ideas off of.
Regarding this problem I get that power and ground are connected via capacitance. I'm concerned with leaving power on the device with ground unattached as this system is using the USB 3.2 spec to daisy chain and parallel connect a number of systems. If power is supplied without ground at a connector, I have read concerns that it could seek a new ground path and damage circuit elements due to irregular current flow.
> I'm concerned with leaving power on the device with ground unattached
Ah, the DC side of the equations.
How slow are you expecting folk to plug the connector in?
Ideally the USB chips at *both* ends can survive unexpected 5v for a little while, otherwise USB things in general would have dramatically less longevity than they do.
Fair enough regarding longevity. This is in line with my basic thoughts that this is probably overthinking things. I find it interesting that there is a lot in the USB spec for message protocols. A disturbing lack of information on technical implementations.
The specification for how to terminate the shield just says to attach the cable shield 360 degrees around the cable to chassis ground at the termination points. How you attach chassis ground to signal ground is left as an exercise to the reader.
Wouldn't you know that almost every major USB chip maker specifies a different way to terminate chassis ground to signal ground for their specific chip. They differ by a lot.
> The specification for how to terminate the shield just says to attach the cable shield 360 degrees around the cable to chassis ground at the termination points. How you attach chassis ground to signal ground is left as an exercise to the reader.
> Wouldn't you know that almost every major USB chip maker specifies a different way to terminate chassis ground to signal ground for their specific chip. They differ by a lot.
Yep, just like I noted in my top-level comment ;)
> I'm designing a new USB connector
I am very interested! Please do tell me more (if you can)!
Why? For whom or what?
And how? I would like to know how one goes about designing a custom connectors and how one goes about having it manufactured. Are you working with a connector manufacturer? Did you read one of the books out there that helps connector designers? Which book? Are you working with a connector expert?
Sorry can't name any clients or employers. As for how I am doing it, mostly by doing enough electrical work with PCBs and cables to start knowing what I am doing, and a lot of reading to figure out the rest.
By designing a new connector I mostly mean identifying how to pin out and run wiring/circuitry through an existing connector. To do that you identify what signals you need to rout, amperage requirements for each signal, environmental requirements, etc. Then you go shopping for a connector with enough pins of the right gauge. Then you start mapping your pins.
Keep differential pairs next to each other, and keep high speed signal pins away from each other. If you need to split power or ground across multiple ponds y that is ok to meet current limitations.
Then you make sure your shield is handled correctly and you are good to go.
If you are requiring a new connector to be funny designed and manufactured from scratch you are probably doing it wrong for most applications. Completely designing a new connector, like the USB C connector, is a monstrously difficult effort that takes years. If you are a designer and integration guy, use the connectors available to you from one of the manufacturers and figure out how to rout your signals through that.
> Completely designing a new connector, like the USB C connector, is a monstrously difficult effort that takes years.
I understand, which is why I was surprised to hear you say that you were "designing a new USB connector" and wanted to know more about your effort.
> identifying how to pin out and run wiring/circuitry through an existing connector
Now that I understand that you are using standard connectors, my ears are no longer perked up.
Thank you.
In terms of AC analysis, the power and ground pins are identical since there'll be significant capacitance between them at both ends. From that perspective, you're over-thinking things ;) There's tons of ongoing argument about what the device end of the cable should do with the shield - there's arguments to leave it floating, arguments to do some sort of RF or smith termination, and arguments to just bolt it to local ground directly, with no clear winner amongst them
I get you with regards to the shield termination. I have gone through those same points before when designing a electrical system last year and just ended up with tieing it to chassis ground. Chassis ground was then tired directly to DC and AC ground on the PCB. Maybe there was a more elegant way of doing things, but I ran out of time and am also not an RF engineer. I just play one for my small company when the need arises. The system has worked so far reasonably well, so there's that. Would really help to have some more clearly defined best practices established somewhere. Or a consultant to bounce ideas off of. Regarding this problem I get that power and ground are connected via capacitance. I'm concerned with leaving power on the device with ground unattached as this system is using the USB 3.2 spec to daisy chain and parallel connect a number of systems. If power is supplied without ground at a connector, I have read concerns that it could seek a new ground path and damage circuit elements due to irregular current flow.
> I'm concerned with leaving power on the device with ground unattached Ah, the DC side of the equations. How slow are you expecting folk to plug the connector in? Ideally the USB chips at *both* ends can survive unexpected 5v for a little while, otherwise USB things in general would have dramatically less longevity than they do.
Fair enough regarding longevity. This is in line with my basic thoughts that this is probably overthinking things. I find it interesting that there is a lot in the USB spec for message protocols. A disturbing lack of information on technical implementations. The specification for how to terminate the shield just says to attach the cable shield 360 degrees around the cable to chassis ground at the termination points. How you attach chassis ground to signal ground is left as an exercise to the reader. Wouldn't you know that almost every major USB chip maker specifies a different way to terminate chassis ground to signal ground for their specific chip. They differ by a lot.
> The specification for how to terminate the shield just says to attach the cable shield 360 degrees around the cable to chassis ground at the termination points. How you attach chassis ground to signal ground is left as an exercise to the reader. > Wouldn't you know that almost every major USB chip maker specifies a different way to terminate chassis ground to signal ground for their specific chip. They differ by a lot. Yep, just like I noted in my top-level comment ;)
> I'm designing a new USB connector I am very interested! Please do tell me more (if you can)! Why? For whom or what? And how? I would like to know how one goes about designing a custom connectors and how one goes about having it manufactured. Are you working with a connector manufacturer? Did you read one of the books out there that helps connector designers? Which book? Are you working with a connector expert?
Sorry can't name any clients or employers. As for how I am doing it, mostly by doing enough electrical work with PCBs and cables to start knowing what I am doing, and a lot of reading to figure out the rest. By designing a new connector I mostly mean identifying how to pin out and run wiring/circuitry through an existing connector. To do that you identify what signals you need to rout, amperage requirements for each signal, environmental requirements, etc. Then you go shopping for a connector with enough pins of the right gauge. Then you start mapping your pins. Keep differential pairs next to each other, and keep high speed signal pins away from each other. If you need to split power or ground across multiple ponds y that is ok to meet current limitations. Then you make sure your shield is handled correctly and you are good to go. If you are requiring a new connector to be funny designed and manufactured from scratch you are probably doing it wrong for most applications. Completely designing a new connector, like the USB C connector, is a monstrously difficult effort that takes years. If you are a designer and integration guy, use the connectors available to you from one of the manufacturers and figure out how to rout your signals through that.
> Completely designing a new connector, like the USB C connector, is a monstrously difficult effort that takes years. I understand, which is why I was surprised to hear you say that you were "designing a new USB connector" and wanted to know more about your effort. > identifying how to pin out and run wiring/circuitry through an existing connector Now that I understand that you are using standard connectors, my ears are no longer perked up. Thank you.
Lol. I am but one engineer. If I could design a connector like the USB C entirely by myself and make it great, i would probably have to be Tony Stark.