DS90UH948-Q1: EMI noise in 45MHz-242MHz

Roy Chou1

Genius 17210 points

Part Number: DS90UH948-Q1

Hi team,

We have EMI test by using 947/948 and the result is showing as below.

STP/1920*1080_60frame(947 pattern gen)/PCLK=150MHz

RE310 frequency range : 45MHz-242MHz

We find that we have 101MHz and 172MHz noise on board, but we have no idea why 947/948 create these two noise, below is my condition

1. Only have 101MHz noise when 947(power on) and 948(shut down-close the power)

2. There is no noise of 101MHz/172MHz noise when 947(PDB pull low) and 948(shut down-close the power)

3. There are 101MHz/172MHz noise when 947(power on) and 948(power on)

4. There is no noise of 101MHz/172MHz noise when 947(PDB pull low) and 948(power on)

For above question, could you give me some comments?

And could you also let me know the difference between using PDB pull low and power off the serdes?

Regards,

Roy

over 5 years ago

0 Charley Cai over 5 years ago

TI__Genius 12866 points

Hi Roy,

When you pull PDB low, the device is in a power down mode and will still draw some currents. In the device is power off, the device is not active at all.

Do you see a difference between PDB low and power off?

Can you share a picture of the setup you are using for EMC testing?

0 Roy Chou1 over 5 years ago in reply to Charley Cai

TI__Genius 17210 points

Hi Charley,

Do you see a difference between PDB low and power off? (No)

Could you let me know which function will still draw some currents from SerDes.

For setup, it's ford spec which is called FMC1278 RE310.

Did you face 101MHz/172MHz noise before?

Roy

0 Roy Chou1 over 5 years ago in reply to Roy Chou1

TI__Genius 17210 points

0 Charley Cai over 5 years ago in reply to Roy Chou1

TI__Genius 12866 points

Hi Roy,

We actually fully pass Ford RE310 with 947 and 948.

Due to confidentiality, I will take this offline.

Best Regards,

Charley Cai

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DS90UH948-Q1: EMI noise in 45MHz-242MHz