V-by-One HS 8:2 switch

Rifo,

I believe the V-by-One HS signals are ~3Gbps LVDS signals. This means you will need to look at our high speed differential switches like you have mentioned with the TS2PCIE412 and TS3DV642.

I am confused about the solution you are looking for "choose 2 out of 8?" Can you provide a diagram of what you would like to achieve?

Thank you,
Adam

Hello Adam,

Thanks a lot for your answer.  I have provided a block diagram below. My application is about analyzing 4K2K video source. Output of the video source is 8 channels of Vby One data. I can only analyze two channels at a time so I thought of multiplexing channels at a time. 

Do you think that cascading like this would pose a problem? or maybe there are other alternatives that would make more sense.

thanks a lot

rifo

Rifo,

The TS3DV642 can only accept 6 differential channels at a time so the solution above will not work as drawn.

Any time you cascade a device you will have insertion loss each time a signal goes through a switch due to the impedance of the switch.  You can see the impedance in the Ron and Con specifications in the datasheet.

Let me know what you think about using two TS3DS10224 devices.  This can be used as a differential 1:4 mux if you can get away with using a 1.2GHz device.  (what is the datarate you need to pass)

Hello Adam,

Thanks a lot for the TS3DS10224 suggestion. I have calculated my required according to the following calculation

To display a 4k resolution at 60Hz, the video interface (HDMI, DisplayPort) needs to transfert 12Gbits/second of data:

– bit_per_channel = 8

– num_channels = 3 (RGB)

– resolution = 3840 * 2160

– 60Hz = 60 times per second

– bandwidth = 3840 * 2160 * 8 * 3 * 60

– bandwidth 4k@60Hz = 11.94 Gbits/sec

so to display a 4K resolution at 60Hz, 12Gbits/second of data needs to be transferred, there are 8 available channels,

hence for each channel  12 / 8 =  1.5Gbits/second 

 

so I think I am okey with using TS3DS10224 and will layout a board for my trials but still my BW requirements will likely increase in the future (e.g. 12bits/channel, higher framerate) so I would also be happy to have a fallback solution with  TS3DV642 (or some other appropriate IC from TI)

I have checked again the datasheet of TS3DV642 and couldn't find differential channel limitation of 6. Below diagram is from the datasheet. There seems to be 8 differential channels. Can you please guide me about this :)

Also, once I have Ron and Con, what should I look into to confirm that cascading won't pose a problem, can you also please guide me about this too?

thanks a lot for your help again Adam,

Hello Adam,

Thank you for your answer. Then I understand that I can cascade two TS3DV642 like shown in my previous post and try to mux the VbyOne signal. Am I right?

thanks a lot

ps: I will also try to get more knowledge about the effects of cascadingn

Yes the cascade architecture you describe above will allow you to select 8 differential signals to map to 2 differential signals .

Adam

Hello Adam,

I have prepared the below circuit, I have tied the unused pins of TS3DV642 to GND. In the datasheet, I didn't see anything related to this. Can you please comment if this is okey to do?

thanks a lot

rifo

Hello Rifo,

Terminating the unused channels to ground is okay. We recommend doing 50 ohm terminations but sometimes this is simply not possible. If you do terminate the unused channels to ground you will need to ensure that at no point is the TS3DV642 allowed to have current running through the switches that exceeds the datasheet specifications. This could happen if you accidentally connected a signal source directly to ground through the TS3DV642.

Regards,
Andrew

Hello Andrew,

I have ordered the PCB and the components. I'll follow up here about the outcome.

I made a mistake though :/ somehow I connected the pin 30 of TS3DV642 ( NC) to GND :/

Do you think that I will be able to get away with this? or should I do some rework on the PCB around that pin?

thank you for your help
rifo

Hello Rifo,

As long asyou don't dump current through the switch to ground at any point it will likely be okay. I would recommend testing before you think about respining the board.

Regards,

Andrew