DS90UB948-Q1: Can 948 have two different video source?

Sherry Liang

Part Number: DS90UB948-Q1

Dear team,

My customer wants to reserve two designs on one display PCBA to connect two different hosts. One host is a USB interface, and the other is an HSD interface. So there are two LVDS INs, but they do not exist at the same time. That means they choose 2-lane input, but every time there is only one lane(RIN0 or RIN1) works, and single link OpenLDI output. Is this feasible?

Thanks & Best Regards,

Sherry

over 4 years ago

0 Charley Cai over 4 years ago

TI__Genius 12866 points

Hi Sherry,

That wont be possible. The picture you show is for single serialzier dual FPD-Link mode operation.

Depends on the bandwidth, you may be able to find a high speed mux and place the mux in front of the 948 to switch inputs.

The other option would be to layout the board in a way that you can use AC coupling cap to change which connector is routed to the 948.

Best Regards,

Charley Cai

0 Sherry Liang over 4 years ago in reply to Charley Cai

TI__Genius 10255 points

Hi Charley,

Thanks for your reply!

About the second option, you mean as below? If I use RIN0, remove RIN0's AC capacitor and keep RIN1's cap?

Thanks & Best Regards,

Sherry

0 Charley Cai over 4 years ago in reply to Sherry Liang

TI__Genius 12866 points

Hi Sherry,

No, you would always need to use Port 0 to connect to both inputs.

But in layout, you can have a tri-pad to redirect the signals from input 1 or input 2.

For example, the yellow boxed caps can to routed to input1 and the green boxed cap can route to input 2. During manufacturing, you can depopulate one set of caps to pick input source.

0 Sherry Liang over 4 years ago in reply to Charley Cai

TI__Genius 10255 points

Hi Charley,

Thanks for your reply!

But the picture you uploaded seems to fail to be loaded, I can't see it.

Could you please upload it again through below button. Thanks!

Best Regards,

Sherry

0 Charley Cai over 4 years ago in reply to Sherry Liang

TI__Genius 12866 points

Sorry about that. Please see attached.

0 Sherry Liang over 4 years ago in reply to Charley Cai

TI__Genius 10255 points

Hi Charley,

Thanks for your reply!

In the green box, the cap is perpendicular to the trace. This will impact the high speed signal transmission in my understanding, right?

Thanks & Best Regards,

Sherry

0 Charley Cai over 4 years ago in reply to Sherry Liang

TI__Genius 12866 points

Hi Sherry,

The effect should be minimal when the layout is done correctly. You can use Anti-pad under the cap to ensure there's minimal discontinuity.

You can also try to run short traces (less then 2 inchs on FR4) to get better loss.

Best Regards,

Charley Cai

0 Sherry Liang over 4 years ago in reply to Charley Cai

TI__Genius 10255 points

Hi Charley,

Can I put the green box caps and yellow box caps in the same place? That means place these two boxes overlapping, is it ok?

Thanks & Best Regards,

Sherry

0 Casey McCrea over 4 years ago in reply to Sherry Liang

TI__Guru** 103215 points

Hello Sherry,

Yes, correct this is called a shared pad layout and is ok to implement. We have done this before on our PCB designs and the performance was very strong.

Best Regards,

Casey

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DS90UB948-Q1: Can 948 have two different video source?