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LMH1981: Don't get any signal on VSOUT when Tri-Level Sync generator is applied on input in 1080p or 720p

Christophe Persoz
Prodigy 10 points
Part Number: LMH1981

Hello,

I'm experimenting a bit this IC, but when I'm applying a Ref Genlock source on input which generate a 1080p25 broadcast Tri-Level Sync (AJA Gen 10) on input, I only get frame line pulse on HSOUT, but nothing on VSOUT for VSYNC pins.

I also tried to put the ref generator in 1080i50 mode, and see if I'mg getting signal on OEOUT, but like VSOUT, the output remains silent, 0v for OEOUT and 5v for VSOUT. Here also, only the HSOUT is giving a proper push output signal like expected.

So I wonder if the IC behave correctly, or if I'm doing something wrong. Referring to the reference data sheet, those outputs VSOUT / OEOUT should output correct pulses and edges when a trig-level ref generator is applied on input. Maybe those output only behave correctly when a complete HD-SDI signal is applied. I haven't tried yet as I do not have the right generator to feed the circuit with a 1080p25 HD-SDI signal.

If someone can explain me where I am wrong here, I'm really interested.

Thanks a lot!

  • 0
    TI__Guru** 107300 points

    Hi Chris,

    We are not sure if this is the behavior of this device. 

    Although our team took over the support of this device but we are not specialized in video product. We haven't experience this device with a non-video signal.

    Sorry that we are not able to help.

  • 0 in reply to Noel Fung
    Prodigy 10 points

    Hello,

    Thanks for your reply even if a bit disappointing...

    If TI is manufacturing and developing an IC compatible with Tri-Level Sync signal, TI should be able to answer this - otherwise, who can answer this?

    Best regards

  • 0 in reply to Christophe Persoz
    TI__Guru** 107300 points

    Hi Chris,

    I agree our support to this device is not ideal, this part is over 15 years old, we have lost all the people who know this product well. In addition, our team doesn't have the specialized video test equipment that allow us to do a thoughtful evaluation. 

    once again, apologies for not able to help.