DP83869HM: signal amplitude symmetry test fail

Hi,

May I ask the compliance test setup that you are using?

• what is the cable length that you are using for the compliance test?
• what type of cable are you using for the compliance test
• the fixture board that you used for compliance test?

If possible, could you share the schematic?

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Thank you,

Hillman Lin 

Cable1：CAT5E ，15cm；

Cable2：UL1571，15cm；

Fixtures：N5395C

Recently，we test 1000 Base-T，Point A、B Peak Output Voltage also failed ，

While we set Reg 0x1D5 = 0x476，the test passed.

So，100 base have the Reg used to adjusting performance ?

schematic：

Hi,

From the report, it seems like it is 1000BaseT compliance test report. Programming register 0x01DF is required to pass the VOD compliance test for 1000BaseT.

Based on your setup, I see there is an extra cable 2 to the fixture. If possible could you remove the cable 2 below and connect DUT directly to cable 1?

It seems like the schematic picture is not too clear. If possible, could you send a better picture on the schematic. Is there any resistors value on the MDI lines?

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Thank you,

Hillman Lin

Hi,Hillman

Thank you for your reply！

The problem we need to solve is the 100base failed at the top of the forum.

Then the 1000BaseT compliance test is Comparative testing for problem-solving.this also Failed,but we Programming register 0x01DF Solved the 1000-T problem and passed the test.

So,if have the Reg used to adjusting performance for 100M.4011.DP83869.pdf

PS:

1、extra cable 2 can not removed;

2、resistors value is 3.9Ω . while replace 0Ω The test results are even worse；

Hi Hillman Lin,

Many thanks for your following and answer.

A big sorry that my words make you misunderstand , now i want to express more clearly about my problems.

Pls come back to the beginning of our communication. We want to solve the problem“When we use DP83869 to test 100M Ethernet, the signal amplitude symmetry test was failed.”-- the specification range should be:0.98<->1.02,but our result is 0.949.

Actually,we want to know if it is possible to set a register to achieve the correct specification range:0.98<->1.02? because we did a test for 1000base-T under the same compliance test setup,it’s workable.

Many thanks for your time.
Best regards
Jun

Hi Jun,

0x01DF are only used for 1000Base-T communication.

However, I believe this register will not have any effect on 100Mbps communication. You can try it out on your 100Mbps compliance test setup and see if that help on your application.

DP83867PHY should 100Base-TX compliance test with big tolerance. Here are some recommendation to help on your 100Base-TX compliance test:

Based on your setup, I see there is an extra cable 2 to the fixture. If possible could you remove the cable 2 below and connect DUT directly to cable 1?

It seems like the schematic picture is not too clear. If possible, could you send a better picture on the schematic. Is there any resistors value on the MDI lines?

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Regards,

Hillman Lin

Hello Hillman Lin,

Hope you have a nice day.

Yes, you're correct. 0x01DF register is not workable in 100base. In the datasheet , it remarks 0x01DF register is for 1000Mbps, but not write any register for 100Mbps and i want to know if there're any register for 100Mbps from your experiences??

At the beginning,“DP83869 to test 100M Ethernet, the signal amplitude symmetry test was failed.”-- the specification range should be:0.98<->1.02,our result is 0.949,there’s 70mV tolerance.

With your recommendation, we did some tests today and i want to tell you the results as below:
1.We change the lengths of the cable2 ,such as 20cm,30cm.Meanwhile,we also try to change the materials of the cable2 ,both test results are all around 0.95*, there’s still 53~55mV tolerance.
2. If we connect DUT directly to fixture and only bypassed cable2,the result is 0.96 , the tolerance is 50mV.
3.If we connect DUT directly to fixture and ,bypassed both cable2 and the transformer T, the result is 0.963, tolerance is 42mV.

Resistors value is 3.9Ω . when we replaced 0Ω ,the test result was worse.

Above tests seems like a little better in the result,but can't meet our requirements. The most important thing is that we can't remove the cable2 in our actual application.

Want more guidance from you .

thousand of thanks.

Jun

DP83869-schematic.pdf

Hi,

Thank you for sharing the detail information.

I see that you have a ESD diode. Could you also try to remove the ESD diode and see that help with your compliance test.

We see that ESD diode have effect on compliance test for other customer before.

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Thank you,

Hillman Lin

Oh，i forgot to share, there has been no change for remove the ESD diode。

Hi,

If possible, could you share the test report with the failing waveform. 

We also have layout checklist. If possible, could you also take a look mainly on the MDI lines and see if any variation?

5466.Industrial_PHY_Layout Review Checklist.xlsx

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Regards,

Hillman Lin