LMH0397: How to center the eye diagram

Romain Boullet

Part Number: LMH0397
Other Parts Discussed in Thread: LMH1297EVM

Hi,

I am making some measurements of the input video signal of the LMH0397 and I can't see the transitions 0 to 1 and 1 to 0 on the eye diagram that I get from the SMBus.

Is there any registers to set to get the diagram centered ? For information the input signal is SDI 720p50.

Regards.

10 months ago

0 Nick Peabody 10 months ago

TI__Expert 5910 points

Hi Romain,

From where did you get the image you sent above? If you use the SigCon Architect GUI you will be able to visualize these transitions as well.

Best Regards,

Nick

0 Romain Boullet 10 months ago in reply to Nick Peabody

Prodigy 10 points

Hi Nick,

I just get the EOM data from the SMBus as described in the SNLU225B chapter 3.9.1.1.

Then I use Excel to color the 64x64 cells according to the number of hits.

I can not use SigCon Architect GUI because I don't have direct access to the LMH0397 SMBus (I just can access by SSH to the SoC that controls the LMH0397).

Thanks

0 Nick Peabody 10 months ago in reply to Romain Boullet

TI__Expert 5910 points

Hi Romain,

Please allow some time for me or my colleague to comment on this.

Best,

Nick

0 Nasser Mohammadi 10 months ago in reply to Nick Peabody

TI__Guru* 93670 points

Hi Romain,

1). Please refer to the programming guide. You can read HEO and VEO values. This give you a good indication of if your 64X64 eye diagram dump is correct.

2). It would be a good idea if you could please get one LMH1297EVM. This comes with GUI and through GUI you can make the same measurement.

3). Please note link below discussing how to reconstruct 64X64 eye diagram:

https://www.ti.com/video/5797181755001?keyMatch=HOW%20TO%20RECONSTRUCT%20EYE%20DIAGRAM

Regards,Nasser

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LMH0397: How to center the eye diagram