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DS90CR288A Tri-state outputs

Aaron Ridinger
Intellectual 490 points
Other Parts Discussed in Thread: DS90CR288A, DS90CR287

Hello,

I am designing an HD video input interface that will have multiple videos connected to an input bus.  The HDMI and component video receivers have tri-state outputs, but the LVDS receiver/deserializer - DS90CR288A - does not.  I was looking at buffers such as the 74LVC245A, 74ALVC245, or 74LVC16245A, however I am concerned with these devices being fast enough.  The HD signal is YCbCr 4:4:4, with a clock rate of 74.25MHz.  This gives a period of 13.5ns, and the above listed buffers have maximum delta(t)/delta(V) of 5 to 10ns and typical propagation delays of ~3ns.  Would any of these buffers work for this application, or are there other options?

Thanks in advance,

Aaron

  • 0
    TI__Guru* 93670 points

    Hi Aaron,

    Just came across this post. Sorry for the long delay.

    What is important is the setup and hold time(RSRC, RHRC, TSTC and THTC). Based on operating at 75MHz  would your system be able to gurantee these requirements? The numbers in the data sheet are for 85Mhz so as long as we can meet these we should be fine. I would not be worried about dv/dt or prop delay as long we can meet the setup/hold time requirement.

    Regards,,nasser

  • 0 in reply to Nasser Mohammadi
    Intellectual 490 points

    Hi Nasser,

    Thanks for the response.  To confirm, my concern should be less with the buffer, but more with how the DS90CR288A interfaces with the rest of the system?  I did not see any setup and hold parameters in the buffer datasheets.

    The outputs from the DS90CR288A will pass through the buffer and into the HDVPSS of a DM8168. Since the setup time of the DS90CR288A (RSRC=3.5ns) is less than the DM8168 (tsu=3.75ns) and the hold time of the DS90CR288A (RHRC=3.5ns) is greater than the DM8168s (th=0ns) it should be fine.  Is this correct?

    Thanks,

    Aaron

  • 0 in reply to Aaron Ridinger
    TI__Guru* 93670 points

    Hi Aaron,

    I believe you have DS90CR287 transmiting video to DS90CR288A.

    In the buffer data sheet you may not see the setup/hold time but based on the timing analyses/propagation delay and Tx/Rx clock timing you should be able to see if you can meet setup/hold time for both DS90CR287 and DS90CR288A.

    On DS90CR287, using TxCLKin, we need to make sure the setup and hold time are satisfied so we can transmit the video reliably.

    On DS90CR288A side, on the rising edge of the RxCLK Out the setup and hold time are 3.5nS. Given this parameter, please make sure your system can reliably interface to DS90CR288A. 

    Regards,,nasser