DS90UH948-Q1: Eye diagram spec

Hi Roy,

Each of 947 and 948 has it own specs. There are several way that you can measure the eye diagram.

1. You can measure the eye diagram from 947 by using the high speed oscilloscope.
2. You can measure the eye diagram from end-end system by measuring at the CMLOUT after AEQ per your mentioned.
3. You can use the MAP tool locates in the ALP to monitor the eye opening.
4. To measure the back channel eye diagram, you need to disconnect serializer side and attach the high speed probe on RINx of the 948.

Hope this helps. Let me know if you have further questions.

Aaron

Hi Aaron,

1. You can measure the eye diagram from 947 by using the high speed oscilloscope.
   1. Do you mean that I could measure the Rin0 and Rin1 of 948 directly by using high speed oscillator?(measure eye diagram before AEQ) 
   2. Could you let me know what is accept Eye Width and Eye Height in this measurement?  
2. You can measure the eye diagram from end-end system by measuring at the CMLOUT after AEQ per your mentioned.
   1. Could you tell me what is the acceptable eye diagram by measuring at the CMLOUT? (image that I attached previous page?)
3. You can use the MAP tool locates in the ALP to monitor the eye opening.
   1. I use the ALP and refer to SNLA301, if I could match fig.6 in SNLA30, we could say that is acceptable eye diagram?
4. To measure the back channel eye diagram, you need to disconnect serializer side and attach the high speed probe on RINx of the 948.
   1. Could you let me know what is accept Eye Width and Eye Height in this measurement?

Thank you.

Regards,

Roy

Hi Aaron,

Excuse me. Do you have any comments?

Regards,

Roy

Hi Roy,

I reviewed the datasheet for both 947 and 948. I do not see eye height and width specification.

1. I meant you can measure the eye diagram from 947 -> oscilloscope not through 948.
2. You can also measure the eye diagram from the CMLOUT after AEQ. I would recommend to use the MAP tool to analyze and understand the signal integrity. This is very similar to CMLOUT. There is no mathematical represent to the MAP tool. Basically, if you see the larger green area representing in digital, this indicates the larger eye.
3. Every device is different. I wouldn't recommend to use the figure 6 as your reference.
4. Again, I do not have the eye height and width.

Aaron

Hi Aaron,

I still have some question about measuring eye diagram before AEQ.

You can measure the eye diagram from 947 by using the high speed oscilloscope.

Do you mean that I could measure the Rin0 and Rin1 of 948 directly by using high speed oscillator?(measure eye diagram before AEQ) Could you let me know what is accept Eye Width and Eye Height in this measurement?  

I meant you can measure the eye diagram from 947 -> oscilloscope not through 948.

I will have no idea which point should I measure if I would like to get eye diagram before AEQ. Is below test point correct?

Do we need to measure this point? or just need to measure CMLout to check if FPD-link is healthy or not?

Regards,

Roy

Hi Roy,

Sorry for the confusion. If you measure the eye before 947, this eye will be without AEQ, which mean the 948 is not connected to 947. If you want to measure the eye with AEQ, then you need to measure at the CMLOUT or use the MAP tool embedded in the ALP sofware. The MAP tool is the best method for you to analyze the signal integrity.

My suggestion is to connect 947 to 948, and use the MAP tool. The app note that you showed me last time should be able to guide you obtaining the eye.

Hope this helps.

Aaron

Hi Aaron.

I think that I got your point.

We should concern CMLOUT's eye diagram because it's the real data in 948.

I asked measuring the 948 Rin side because customer would like to check if their cable use is good or not. So they didn't want to measure the eye diagram after AEQ. 

Regards,

Roy