Linux/DS90UB913A-Q1: Failed on EFT(Electrical Fast Transient) Test

user3528687

Part Number: DS90UB913A-Q1
Other Parts Discussed in Thread: DS90UB914A-CXEVM

Tool/software: Linux

Hello,

DS90UB913A and 914 are used in our camera design. And 5M cable is used to connect these two chips. The camera works OK. But the image is disordered during the EFT(Electrical Fast Transient) Test when it goes up to 500V. In fact, it needs to pass 2KV in the application. The case of camera and receiver is metal and is connected to GND. So the whole system has one GND. We believe the shielding is fine.

Do we need to add some common mode filter on the signal? If so how to add that?

Does anyone have idea on this issue?

Thanks,

Bob

over 7 years ago

0 Davor Glisic over 7 years ago

TI__Expert 8165 points

Hello-

The following are some general guidelines:

-Use good connection between shield and the chassis at the connector so the ground transition is smooth and continuous.

-Ensure that all supplies within the board are well-coupled to the system ground so supply and ground track transient injected signals well

-Common mode filters are an option too. We suggest placing it on the deserializer side after the AC-coupling capacitors (looking from the device RIN pins).

Regards,
Davor

0 user3528687 over 7 years ago in reply to Davor Glisic

Prodigy 40 points

Davor,

Thank you for your reply.

For current design, single-ended signal is used, with coaxial cable.

In terms of the common mode filters, is it only for differential signals? If yes, what are the parameters of the desired filters? If the filters can also work with single-ended signal, how to config the filters?

Best Regards,

Bob

0 Davor Glisic over 7 years ago in reply to user3528687

TI__Expert 8165 points

Hello-

The filter (CMC) may be used with single-ended signal as well. If we reference DS90UB914A-CXEVM schematic (www.ti.com/.../snlu135b.pdf , page 25), one CMC winding can be connected between the AC-coupling capacitor (C6) and the note PoC filter connects to the trace. The second winding would be connected between the second AC-coupling capacitor (C7) and the 50-ohm termination resistor.

Regards,
Davor

0 Daniele Loperfido over 7 years ago in reply to Davor Glisic

Prodigy 60 points

Which CMC filter do you suggest?

0 user3528687 over 7 years ago in reply to Davor Glisic

Prodigy 40 points

Davor,

The CMC should be used for both sides, transmitter(913) and receiver(914). Is that correct?

Thanks,

Bob

0 Davor Glisic over 7 years ago in reply to Daniele Loperfido

TI__Expert 8165 points

Hello-

Murata DLW21SZ900HQ2 would be an option.

Regards,
Davor

0 Davor Glisic over 7 years ago in reply to user3528687

TI__Expert 8165 points

Hello-

You can start placing a CMC on the 914 side only and see if there is improvement. Adding additional decoupling on the VDD pins could also help.

Regards,
Davor

0 user3528687 over 7 years ago in reply to Davor Glisic

Prodigy 40 points

Hi Davor,
Here is the update on this issue. CMC's were added on both sides, 913 and 914. Actually two kinds of CMC's were used, DLW21SN900HQ2L and DLW21SN261XQ2L. It is still single-ended scheme. The results are different. There is almost no improvement when using DLW21SN261XQ2L. While it improves a lot when using DLW21SN900HQ2L. But the issue is still there. There is 40% chance to see the image mis-aligned even tested in 500V condition. And it is similar for 2KV. Do you have any suggestion on this? Do we need to try other CMC? Or we have to turn around to seek differential scheme?

Thanks,
Bob

0 Davor Glisic over 7 years ago in reply to user3528687

TI__Expert 8165 points

Hello Bob,

Trying other CMCs would give you good data points (e.g. DLW21SN121HQ2L). Are different connectors or cables an option? Suggest reviewing the following training sessions:

training.ti.com/common-connectors-and-cables-automotive-applications

training.ti.com/line-and-common-mode-chokes-use-and-effect-transmission-channel

Regards,
Davor

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Linux/DS90UB913A-Q1: Failed on EFT(Electrical Fast Transient) Test