LMH1228: LMH1228 with Unstable/shaky image

Marcelo

Can you please share your schematic for review?

Thanks

David

David

I'm so sorry but I can't to share my design schematic because this is a project for a customer.

Marcelo

Any chance you can accept my friendship request so you can send me the design file in a private E2E message?

Thanks

David

David

Why do you believe that if I send you my design schematic could you to help me?

Marcelo

Are you seeing the unstable image at the first LMH1228 or the second LMH1228 output? What is the data rate you are trying to support with this design?

Thanks

David

David

Sometimes the unstable image occurs at the first output, sometimes at the second output.

The data rate is 4K 50fps, 4K 59.94fps and 4K 60fps.

Thanks

Marcelo

Marcelo

Do you have access to the LMH1219 and LMH1228 registers and programming guide? 

I would like to start with the LMH1219 IN0 first. The LMH1219 has an on-chip eye opening monitor (EOM) which can be used to analyze, monitor, and diagnose the performance of the link. The EOM operates on the post-equalized waveform, just prior to the reclocker. Therefore, it captures the effects of all the equalization circuits within the receiver. With this EOM feature, you can also read the horizontal and vertical eye opening. Can you see if there is a difference in the horizontal and vertical eye opening between a stable and an unstable image? For detail on EOM and horizontal and vertical eye opening, you can refer to sector 3.12 of the LMH129 programming guide.

Thanks

David 

David,

Thanks for the information.
I had already considered that possibility, but since the oscilloscope doesn't measure frequencies above 100 MHz, I ruled it out.
What I did was increase the VOD and De-Emphasis values ​​so the signal could be delivered with more power.
I’ve left the equipment running on the test bench to see how it behaves after a period of use.
Once the tests are finished, I’ll get back to you with an update.

Thanks

Marcelo

Hi David

Following up on my last message, here are my results:

1- The code structure written to configure the LMH1219 and LMH1218 was incorrect; I have fixed it;
2- I inserted coupling capacitors into the LMH1219 traces that connect to the fiber optic transceiver;
3- Using jumpers, I changed the transceiver signal input on the LMH1218 from IN0 to IN1, but there was no change; the 4K 50, 59.94, and 60fps signals still failed to open;
4- When testing with equipment from another manufacturer, the 4K signal works normally, as I previously reported;
5- I checked the documentation for the TIDA-00428 development board, and a diagram on the very first page caught my eye, making me wonder if I might have made a conceptual error in the design...

I spoke with my client regarding a previous message where you suggested I send the schematic to your private email address. If it is still possible, please let me know your email address so I can send the schematic to you; if you agree, we can continue discussing this matter via email.

Thanks

Marcelo