CCS/LMH0324: EQ performance adjustment for LMH0324

boer.deng

Part Number: LMH0324
Other Parts Discussed in Thread: LMH0302, LMH1219, LMH1219EVM

Tool/software: Code Composer Studio

We have customer feedback that our SDI allocator scheme does not transmit as far as Semtech's scheme.Said that in the same use environment our scheme has noise will flash.

Semtech's scheme is GV7704+GS2989. Later, we thought it was a problem caused by the drive, so we made a scheme of LMH0324+GS2989, but the effect is still good

It is not as good as LMH0324+2*LMH0302, so we estimate that the EQ performance of LMH0324 is not so good.See if you can adjust anything to improve it

Performance, thank you!

over 6 years ago

0 Nasser Mohammadi over 6 years ago

TI__Guru* 93670 points

Hi Boer,

Please clarify, are you saying if we use LMH0324+GS2989 cable reach is the same as when we are using GV7704+GS2989?

Regards,,, Nasser

0 boer.deng over 6 years ago in reply to Nasser Mohammadi

Expert 1085 points

The transmission distance of LMH0324+2*LMH0302 scheme is not as good as that of GV7704+GS2989. At the very beginning, I suspected that it was the driver output signal problem, so I made another LMH0324+GS2989 scheme. The publishing distance is still far from that of GV7704+GS2989.How can we adjust the EQ performance of 0324?

0 Nasser Mohammadi over 6 years ago in reply to boer.deng

TI__Guru* 93670 points

Hi Boer,

LMH0324 is an adaptive equalizer and performance cannot be adjusted.

Regards,,, Nasser

0 boer.deng over 6 years ago in reply to Nasser Mohammadi

Expert 1085 points

At present, I use standard cable with 2.97g transmission rate. The transmission distance is very close. What is the possible reason?It is about 100m. I hope to help you with the analysis. Please refer to EVM for the schematic diagramCron.pdf

0 Nasser Mohammadi over 6 years ago in reply to boer.deng

TI__Guru* 93670 points

Hi Boer,

I checked your schematic:

1). Please confirm R4 is not loaded. We want to make sure OUT_CTRL is floating(no pullup or pull down resistor).

2). Please make sure R5 is loaded and R6 is not loaded.

3). Please clarify what you mean when you say 100m. Does this mean your cable reach is 100m of standard B1694A cable?

Please check these and let me know. Based on your result, we may have one more experiment to run.

Regards,, Nasser

0 boer.deng over 6 years ago in reply to Nasser Mohammadi

Expert 1085 points

Thank you for your reply.

1. At present, R4 R6 NC, R5 welding 10K, the phenomenon is still not improved

2. Compared with GV7704 scheme, under B1694A cable, the distance reaches about 120m, and the transmission of LMH0324 scheme highlights noise and flash breaks, while GV7704 can also be transmitted stably at 200m.

What else can you do to improve the performance of LMH0324?

0 Nasser Mohammadi over 6 years ago in reply to boer.deng

TI__Guru* 93670 points

Hi Boer,

It would be a good idea if you can get a LMH1219 evaluation board and evaluate cable reach. We get the same cable reach as noted in the data sheet. Do you have return loss measurement result?

Regards,, Nasser

0 boer.deng over 6 years ago in reply to Nasser Mohammadi

Expert 1085 points

Are there any other measures to improve circuit performance?

0 Nasser Mohammadi over 6 years ago in reply to boer.deng

TI__Guru* 93670 points

Hi Boer,

I had provided comments related to your schematic. Also, it would be a good idea to use LMH1219EVM to correlate with your cable reach performance. Using LMH1219EVM is very important since this could tell us if the issue you are seeing is related to your pcb or the cable you are using.

Regards,, Nasser

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CCS/LMH0324: EQ performance adjustment for LMH0324