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elessargr , 12-18-2024, 08:22 PM

Hello everyone,
I am new to the world of PCB so please bare with me if I ask any stupid questions.

I am working on a project that I would need to use a USB-C 3.0 (to the host/lapto) with two downstream USB ports. (one 3.0 and one 2.0).
Power would be provided to the PCB though the USB-C to the host.
I was able to find this https://www.ti.com/lit/ug/tidu428/tidu428.pdf?ts=1734553136810 but they utilizing USB-A connectors instead of USB-C.

The main question I have is,
If I have a USB-C 3.0 connection to the host do I need to use a USB MUX?
The USB-C cable should be able to operate when plugged-in to the PCB on both directions.
So if I loop the pairs together (like A2/B2, A3/B3, etc) this would not work and require a USB MUX as addition?

I can share the schematic I have already if needed.

Appreciate any help you guys can provide.
Thanks again!

ElessarGR

QDrives , 12-18-2024, 10:38 PM

First of: USB-C is the connector, USB 3.0, 3.1, etc. is the standard.

"*I would need to use a USB-C 3.0 (to the host/lapto) with two USB ports. (one 3.0 and one 2.0). *" -- Do you mean a hub with two downward ports?
"*The USB-C cable should be able to operate when planed to the PCB on both directions.*" -- "planed"?? You mean plugged-in?
https://www.edn.com/providing-usb-type-c-connectivity-what-you-need-to-know/

elessargr , 12-18-2024, 10:40 PM

hi QDrives!
Yes downwards ports (client).
https://www.lcsc.com/datasheet/lcsc_datasheet_2304140030_Texas-Instruments-TUSB8020BPHPR_C179675.pdf

elessargr , 12-18-2024, 10:41 PM

Ops sorry yes I meant plugged-in! Good catch let me correct it

elessargr , 12-18-2024, 10:51 PM

okay so from the edn article if I understand correct the USB MUX is not mandatory and it depends what the use case is every time.
Like in my case I dont look for DP or above classic/normal power transfer tot he downstream ports.
So even if USB MUX is not installed the USB-C cable regardless the orientation should work.
Am I correct?

QDrives , 12-18-2024, 10:59 PM

I have never done USB 3, C or other hubs.
All I know is that I often see a mux in the schematics as well. But this is mostly here and they have problems...

elessargr , 12-18-2024, 11:13 PM

Until now I have seen it one or two time on some schematics and because I am a newbie on this world hence why I ask. You guys definitely are more knowledgeable than me on the PCB and schematics!

Lets see if anyone else know about this 🙂

QDrives , 12-18-2024, 11:35 PM

Would it be a cost problem if you add the mux?

elessargr , 12-18-2024, 11:58 PM

I believe by slightly.
I have a prototype that for some reason doesnt work and try to understand if this is the issue.
Also if I add this USB MUX not sure how much space I would need since I try to compress the PCB as much as I can and if it would complicate more the design.

QDrives , 12-19-2024, 12:04 AM

Well... it makes it more complicated and it takes space.
Did you have a mux on the prototype?
The mux is needed to make the USB C connector work in both 'polarities'.

elessargr , 12-19-2024, 09:30 AM

No on the prototypes I haven't used a USB MUX. Currently it doesn't work in any orientation I place the cable in.
Tried a USB-C (host) to USB-C (PCB) and a USB-A (host) to USB-C (PCB).

So doing some research and reading online to see if I can figure it out. Hence why I thought that maybe someone from here would have the expirience with USB 3.0 highspeed and USB-C connector 🙂

QDrives , 12-19-2024, 08:04 PM

If your proto hub without mux is not working in any way, you better first find out why.
Adding a mux will only make things more complicated.

elessargr , 12-19-2024, 08:15 PM

My prototype does not have a mux.

QDrives , 12-19-2024, 08:21 PM

Sorry, meant to write "without mux".

elessargr , 12-19-2024, 08:54 PM

oh, yeah this is what I am trying to find out but I dont have the knowledge or expertise on this kind of subject 😅

elessargr , 12-19-2024, 09:24 PM

I think if I need a USB3 MUX it should be in the orange area.

UTTAM , 12-21-2024, 03:47 AM

use this switch IC

https://www.via-labs.com/product_show.php?id=72

elessargr , 12-21-2024, 09:37 AM

I see that this is EOL.
I was able to find this one
https://www.ti.com/lit/ds/symlink/hd3ss6126.pdf
Going over the datasheet and reading for it

UTTAM , 12-21-2024, 09:39 AM

VL162 or VL163 continue parts

elessargr , 12-21-2024, 09:43 AM

let me check those also!

elessargr , 12-21-2024, 10:05 AM

I cant find this manufacture or its chips to
https://www.mouser.ie/
https://www.lcsc.com/
https://www.digikey.ie/

QDrives , 12-21-2024, 03:36 PM

@elessargr in a sense what @UTTAM states is that you need a mux/demux. However, from what I can see, you should be able to get something working without **IF** you plug in the USB-C connector properly. That is were th mux comes in -- no polarity as it automatically switches over.

elessargr , 12-21-2024, 04:08 PM

Yes this is what I am trying to figure out now. If I can somehow connect a USB-C to the PCB with only one side (A side) connected to see that at least the PCB works. The polarity and all those things with MUX I can fix them later.

elessargr , 12-21-2024, 04:08 PM

new updated version that simplifies things I believe

QDrives , 12-21-2024, 04:58 PM

That one is not going to work, at least not for USB 3.
You got Tx1 and Rx2 connected.

What is the schematic of your first proto?

elessargr , 12-21-2024, 05:26 PM

its this one
https://discord.com/channels/1119543365546029098/1319037171793133599/1319415044223668315

elessargr , 12-21-2024, 05:28 PM

Since I am using the A side only (single polarity) afaik it should work for USB3.0 similar to the USB-A.
https://www.ti.com/lit/ug/tidu428/tidu428.pdf?ts=1734553136810
Page 17

QDrives , 12-21-2024, 11:12 PM

So what do you have on your up stream port? A USB A plug or a C socket?
Your first schematic shows a USB C socket.
As far as I know, with a USB C socket you need the mux to have it work in both positions.
However, if your prototype does not work having the C connector in either position, something else must be checked first.

elessargr , 12-21-2024, 11:30 PM

So on my first schematic and prototype I have a USB-C as upstream (host).
The issue I believe, and from what you guys told me here, is that I am missing the USB MUX for the connection to decide which pair of cables to use. Like there is a negotiation happening when you have a USB-C cable via the CC pins.
So because I dont have a USB MUX and I cant add it to my prototype I will need to modify one/two things on my prototype and convert the USB-C to be like a "USB-A" and see if this would make the prototype work. Hence why I will "cut" the B side of the USB-C to make its a single path connection.
I dont have the right tools to do that though so I need to improvise 😛

QDrives , 12-22-2024, 12:27 AM

No. Without mux it should work in one of the two positions (180° rotation) the USB C connecter is connected.
Like there is suddenly a up and down to it. Up works but down does not.
From my understanding you could not get it to work at all, regardless of the USB C connection.
Another question is: you have USB 2 and 3 on the cable. USB 2 you just connected together. so that sould work.
If USB 2 also does not work, you do not need to look into a mux on USB 3.

elessargr , 01-06-2025, 08:38 PM

hello and Happy New Year!

elessargr , 01-06-2025, 08:39 PM

so I managed to get the USB HUB working but only as USB2.0. So the D+/- seems to be the one actively connected and have it on. Trying now to figure out why I cant bring up the SuperSpeed (USB3.0).

elessargr , 01-06-2025, 08:39 PM

The issue was with one ESD (U4) that was incorrectly connected.

elessargr , 01-06-2025, 08:40 PM

So I just removed it and made a bridge on it.