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Anik , 09-21-2024, 06:37 PM

Hi,
I am working on a project such Display port to HDMI converter. I am using SN75DP149RSBT . I have downloaded its EVM datasheet and I see the dataline is swapped. I have searched on online but have not found anything helpful.

QDrives , 09-22-2024, 02:42 AM

So what is your question?

Anik , 09-22-2024, 05:15 AM

Why the data lane is swapped...!

Anik , 09-22-2024, 07:44 AM

I got it.

Anik , 10-04-2024, 07:18 PM

This is for HDMI to USB 3.2 video acquisition device with USB3.0 and MS2130. The RX and TX pair after the USB dataline controller its crossed. I am not sure does it need to connect RX to TX and TX to RX. I have connected it RX to RX and TX to TX. I have followed this board ( https://github.com/YuzukiHD/YuzukiLOHCC-PRO ), but he used another chip for USB dataline controller.
I am confused will the board work.

QDrives , 10-04-2024, 07:40 PM

I do not see where Tx and Rx are swapped.
I do see that the names assigned in the Yuzuki schematic goes from SSTXM to Tx_P, which in my opinion is incorrect. However, if either the chip or connector is also incorrect, then it becomes working again (not correct, but working).

Anik , 10-04-2024, 07:44 PM

It crossing like this when I go for routing and use RX/RX TX/TX.

Anik , 10-04-2024, 07:48 PM

This is MS2130 datasheet. This also told to use RX to RX and TX to TX.

QDrives , 10-04-2024, 07:48 PM

In the old serial port times, there was DTE and DCE. Connecting DTE to DCE was straight (Tx to Tx) while DTE to DTE needed cross (Tx to Rx).
Is the Tx pin Input, Output or IO? You need to check on both chips.

Anik , 10-04-2024, 07:49 PM

TX pin is output

Anik , 10-04-2024, 07:55 PM

And for HD3SS3220RNHR TX/RX is IO

QDrives , 10-04-2024, 08:11 PM

Your capacitors are on the wrong end.
Tx on Tx.
Page 26 of the datasheet.

Anik , 10-04-2024, 08:17 PM

Ok. its a multiplexer. So if I use the capacitor on the output side will it not work as same??

Anik , 10-04-2024, 08:22 PM

Oh, The RX TX has 2.5V tolerant. So the capacitor need on input side

QDrives , 10-04-2024, 08:22 PM

What do you consider output?
You have the capacitors on the input. The output is to the connector.

Anik , 10-04-2024, 08:23 PM

Yes. The connector is the output.

QDrives , 10-04-2024, 08:24 PM

Check your schematic with the one on page 26 of the datasheet.

Anik , 10-04-2024, 08:26 PM

Yes I have checked,

QDrives , 10-04-2024, 08:27 PM

So where do you see the capacitors in the datasheet and where on your design?

Anik , 10-04-2024, 08:28 PM

Yes. But what willbe the problem if I use another end??

QDrives , 10-04-2024, 08:29 PM

Not so much, but then you still need capacitors on both ends.

Anik , 10-04-2024, 08:35 PM

Ok I will make the same on the page 26.
Also one more thing, Datasheet says this chip doesnot care about the polarity of the RX TX differential pair. Does it mean I can swap any of one?? Like I have swapped TX2 and TX1 for better routing . But kept same for the RX1 and RX2.

QDrives , 10-04-2024, 08:44 PM

I have not worked with this chip, nor anything USB 3.
However, I would say that Tx1 and Tx2 can be swapped, but Rx1 and Rx2 need to swapped then too.
Normally, swapping is selected by the CC pins.

QDrives , 10-04-2024, 08:46 PM

If would study the reference designs on the HD3SS3220 and see how they do thing.
If they swap, you can swap.

If they don't, it is up to you to try or keep it correct.

It almost seems as if you want to keep it all on 1 layer and are therefor afraid to cross lines.

Anik , 10-04-2024, 08:48 PM

Yeah...And got it. I will change the design and will research more about this chip.

Anik , 10-06-2024, 06:57 PM

I have asked on TI support. but I dont have business email so they have not replied yet. I have keep the RX TX on the same line. and they have been swapped so I have used the TX line capacitor in big package and make it like this. Will it be ok for USB3.0 speed

QDrives , 10-06-2024, 07:02 PM

Is it 'safe' to route traces on top below the connector? Usually there is metal there and you cannot safely have copper there other than Gnd/shield.

Anik , 10-06-2024, 07:04 PM

The reference solid GND plane is on the L2. The impedance calculated based on it distance. On the bottom layer reference layer is 3.3V copper pour but not solid.

QDrives , 10-06-2024, 07:05 PM

And the housing of the USB connector is made of what?

Anik , 10-06-2024, 07:55 PM

I dont understand

QDrives , 10-06-2024, 07:59 PM

If the housing of the connector is metal, and is connected to Gnd, you have 2 problems:
- Possible short circuit from the trace to the housing. And **no**, solder mask is **not** an insulator for these purposes.
- Your characteristic impedance should take the housing into consideration too.

Anik , 10-06-2024, 08:00 PM

Really I have not thought about it..!