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DS90CF384A: RxCLKOUT to RxOUT Timing

Vin Parillo
Prodigy 20 points
Part Number: DS90CF384A
Other Parts Discussed in Thread: DS90CR286A

I have a design that uses the DS90CF384A running with an LVDS clock frequency of 33.5MHz to drive an LCD display which requires a min tsetup=4ns and a min thold=2ns.  The DS90CF384A meets this minimum timing requirement with 4.5ns and 4ns, respectively, which the datasheet specifies at 65MHz.  My LCD has now gone obsolete and I am looking at a new LCD.  The new LCD manufacturer which meets all of my requirements mechanically, but is falling a bit short on the timing.  The new display needs a min tsetup=8ns and a minthold=8ns.  I realize that the DS90CF384A specified output timing is not likely dependent upon the RxCLKOUT frequency, but is there any relief in the setup and hold if running at 33.5MHz that might allow me to meet tsetup=8ns and thold 8ns?  I know it's a stretch, but I thought I would ask since I am running out of options.  Other LCD's I have looked at require major mechanical changes in the chassis design.

Is there characterization data available for tsetup and thold at different frequencies for the DS90CF384A?

  • 0
    TI__Mastermind 29655 points
    Hi Vin,

    I have run into a similar question in the past, and there is some characterization data to support operation at 40 MHz for this scenario, which is more representative of your use case than 65 MHz operation.

    It turns out that the lower the operating frequency, the greater the setup/hold time becomes. You can reference this in the DS90CR286A/-Q1 datasheet, which is taken from a very similar silicon to the DS90CF384A. At 40 MHz, the RSRC and RHRC min value is 6.5 ns and 6 ns, respectively, with typical measurements across temperature resting quite tightly between 10-13 ns. I expect this timing to be similar or improve as frequency continues to decrease.

    This may therefore be compatible with the new LCD you are looking at. However, you would need to perform a system characterization with the LCD and DS90CF384A in order to confirm whether timing is suitable.

    Regards,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Prodigy 20 points

    Michael,

    Thank you for your insight.  I plan to run a few systems to the rated temperature extremes as part of my characterization and I'll see how it performs.

    Thanks again,

    Vin