LMH1983 - FIN logic for progressive reference

Kawai

Guru 19785 points

Other Parts Discussed in Thread: LMH1983, LMH1981

Hi Team,

When the input reference is progressive, do you need to keep FIN = High for the LMH1983 auto format detection function to work correctly ?

Or, can we use FIN = Low ?

Best Regards,

Kawai

over 8 years ago

0 Nasser Mohammadi over 8 years ago

TI__Guru* 93670 points

Hi Kawai-San,

LMH1983 looks at the number of 27MHz clocks between HSYNC pulses to detect the incoming video format. For progressive format, i believe, FIN should be kept low.

Regards,,nasser

0 Kawai over 8 years ago in reply to Nasser Mohammadi

Guru 19785 points

Hello Nasser-san,

Below is the screenshot of LMH1981 datasheet. Regarding this figure, LMH1981 seems to output OEOUT(FIN) = High all the time. Could you please confirm ?

Our customer question was that if FIN is ignored for progressive format or not, for LMH1983. If it is limited to either of the logic, please let us know.

Best Regards,

Kawai

0 Nasser Mohammadi over 8 years ago in reply to Kawai

TI__Guru* 93670 points

Hi Kawai-San,

In default mode, EN_AUTOPOL Reg 0x06[3] is set. In this case, the polarity of the H input is automatically detected and it's applied to V and F inputs as well. Therefor as long as EN_AUTOPOL is set, the device automatically detects V & F polarity based on H input.

Regards,,nasser

0 Kawai over 8 years ago in reply to Nasser Mohammadi

Guru 19785 points

Hello Nasser-san,

Thank you for the explanation. I understood that FIN polarity wouldn't matter whether it is kept low or high for progressive format REFIN, as long as EN_AUTOPOL (REG 0x06 [3] = 1). Please let me know if my recognition is wrong.

Best Regards,

Kawai

0 Nasser Mohammadi over 8 years ago in reply to Kawai

TI__Guru* 93670 points

Hi Kawai-San,

Yes your understanding is correct. As long as EN_AUTOPOL is set to 1, FIN polarity does not matter.

Regards,,nasser

0 Kawai over 8 years ago in reply to Nasser Mohammadi

Guru 19785 points

Thank you for checking, Nasser-san.

Best Regards,
Kawai

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LMH1983 - FIN logic for progressive reference