LMH1983: valid reference input and Holdover mode

KAEDE KUDO

Expert 2700 points

Part Number: LMH1983
Other Parts Discussed in Thread: LMH1981

Hello,

I have a question about LMH1983.

[Q]

I have questions about the following D/S sentences.

'If Holdover mode is to be used in conjunction with an analog sync separator, it is best to gate the H,V,and F signals with a signal that indicates if there is a valid reference input.'
D/S, p24, 8.4.4 Free-Run, Genlock, and Holdover Modes

Is this also necessary if the sync separator is LMH1981?

Best Regards,

Kaede Kudo

over 6 years ago

0 Rob Rodrigues over 6 years ago

TI__Mastermind 19780 points

Hi Kaede,

Sorry for the delay.

Yes, the LMH1981 is an analog sync seperator, so the H,V, and F signals should be gated.

Correction, a gating circuit is not needed for LMH1981.

Best Regards,

0 KAEDE KUDO over 6 years ago in reply to Rob Rodrigues

Expert 2700 points

Hi Rob,

Thank you for your reply.
And I'm sorry for my late reply.

OK, I understood H,V, and F signals should be gated.
Can you teach me a reference circuit for Gate processing between LMH1981 and LMH1983?

And I have a one more question.
I confirmed the following Reference Design.
Why signals should not be gated in this?
www.ti.com/.../tidrdk3.pdf

Best Regards,
Kaede Kudo

0 Rob Rodrigues over 6 years ago in reply to KAEDE KUDO

TI__Mastermind 19780 points

Hi Kaede,

My apologies, the LMH1981 does not need to be gated as the H,V,F outputs are guaranteed to hold state when the video input is lost.

You can use the signals as shown in the reference design.

Best Regards,

0 KAEDE KUDO over 6 years ago in reply to Rob Rodrigues

Expert 2700 points

Hi Rob,

Thank you for your cooperation!

I understood it.

Best Regards,

Kaede Kudo

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LMH1983: valid reference input and Holdover mode