HD3SS3220: Swapped TX and RX and swapped channel 1 and 2 - Schematic Review

Hi Sam,

The orientation of the TX/RX lines and the CC lines looks good to me, it's definitely a bit of a messy orientation but I don't believe there will be any issues.

One question I had was these pins on the side:

Are the DIR and ID pins being connected anywhere, or are they just pulled up? The ID and DIR pins are needed to communicate the type-C orientation and whether to be providing VBUS or not to the SOC/Device, but they appear to just be pulled up. I was wondering if these pins are being output to anything, or are just being pulled up.

I also noticed on the PORT pin, you just have it pulled up with the 200KOhm resistor to 5V, but the schematic seems to indicate this is meant to be a DRP connection. With this current pull-up with no other connections, it looks more like a DFP connection. I would just like to confirm what the intention is there.

Additionally, Current Mode is set to 3A. Just want to confirm that as well.

Thanks,

Ryan

Thanks for getting back to me so fast Ryan, 
It is quite a messy orientation but thanks for taking a look at it. 
Right now it is setup as a DFP with the upstream USB connection on pins 6,7,9,10 going to a USB Hub so it is always Host. Power to the USB C connector is controlled by the HUBs power port enables pins. So 5V should basically always be provided to the USB C connector. 
With ID and DIR being outputs we don't think our SoC connected to the HUB needs to monitor these pins, and PORT is pulled high due to it being DFP config.
We used the DFP typical application from the datasheet as our reference. 

Is there something in our circuit that is set as DRP that we should change?

Thanks,

Sam

Hi Sam,

Got it. Unfortunately, if you intending on using a type-C interface, VBUS cannot be sent the whole time. For CC communication, the CC pins need to communicate while VBUS is not being sent, that way they can communicate current mode and attachment. If VBUS is sent during this communication, then it will disrupt the CC pin communication, and will cause issues for device setup, such as not giving the desired current output.

From what I can tell, if you intend to do DFP, I don't see any issues. Just saw some text in the schematic saying DRP.

Thanks,

Ryan

Hi Ryan,

This USB output is only ever going to be plugged into a single known device which is just a USB 3 Micro B port on the other end. So I am assuming because the other end is not USB C. It won't need this functionality. We are really only using the mux to steer the USB 3 signals correctly depending on orientation of USB-C cable.

Sam

Hi Sam,

Sam Wilson said:

We are really only using the mux to steer the USB 3 signals correctly depending on orientation of USB-C cable.

That's an aspect that I think will have issues if VBUS is continually applied. If VBUS is constantly being sent through, the device will not see any detachment, and will not adjust the mux-ing of the device accordingly based on the CC pins. The device will essentially only work in one flip orientation, with the other flip not being able to work properly.

Thanks,

Ryan

Thanks Ryan,

So in the normal case the HD3SS3220 uses the ID pin to tell the processor that its is a host and to enable the VBUS switch? In our case since we have a HUB, I don't know if there is a way to tell the HUB(USB5744) to not deliver power using its PRT_CTRL pin. We are using a TI USB load switch

could we invert the ID pin(since it is low when DFP) and then use that to control if the VBUS load switch is on by connecting it to the enable of the load switch(maybe AND it with the USB HUB's PRT_CTRL also)? So it will be off until ID is pulled low.

Thanks, 

Sam

Hi Sam,

I'm not too familiar with the power switch and hub youre using, but I think it's generally a good idea/theory. As long as VBUS is not being enabled/powered until the ID pin is pulled low via CC communication, then that should I believe solve any issues there.

Please let me know if you have any other questions.

Thanks,

Ryan