LMH1297: Poor Eye Diagram on SDI_IO Compared to SDI_OUT

Nick Peabody

Part Number: LMH1297

Dear Nasser,

Long time no see, how are you ? I hope you are very well?

I've recently been using LMH1297 as an interface chip for optical transmission, and I've had a problem that hasn't been solved:

the quality of the eye diagram is poor (relative to PIN8) when the input port of the LMH1297 is configured as the output.

I suspect it's the influence and interference caused by the internal EQ circuit to the CD circuit, but the EQ function has been turned off, so I don't know if there is any other workaround

Thanks Nasser,

KindRegards!

WangChen.

3 months ago

0 Nick Peabody 3 months ago

TI__Intellectual 2155 points

Hi Wang,

I discussed with Nasser and we wanted to make sure we understood your application.

In the picture above, is the BNC output on the left SDIOUT(PIN8) and the BNC output on the right SDI_IO?

Is the issue is that the SDIOUT eye diagram is poorer than the SDI_IO eye diagram?

Where does the optical module fit into your application? If you could provide a block diagram that would be helpful.

Best Regards,

Nick Peabody

0 chen wang 3 months ago

Prodigy 15 points

Hi Nick,

I couldn't upload an attachment in the forum, so I replied to you in the email.

Thanks.

0 Nick Peabody 3 months ago in reply to chen wang

TI__Intellectual 2155 points

Hi ChenWang,

I responded to your email today.

Best Regards,

Nick

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LMH1297: Poor Eye Diagram on SDI_IO Compared to SDI_OUT