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DS90UB964-Q1: COAX_Input ESD problem

Part Number: DS90UB964-Q1
Other Parts Discussed in Thread: STRIKE

HI:

Now I have some problem.

1.What are the ESD measures for COAX input?

Now I have connected 4 COAX cameras to DS90UB964.ESD level:±8KV,330Ω,330PF.A certain camera image collapses.I have now added an ESD tube with a capacitance of 1pF to the ground on the COAX and use copper foil to wrap the PDD-link on the PCB board,But it doesn't seem to be working.So I need new ESD measures.

2.How to configure registers to forcibly switch between internal and external reference clocks?

I have now removed the external reference clock, but the DS90UB964-Q1 still works.I don't understand if this external reference clock works on ds90UB964-Q1.So does this affect the frame synchronization signal?

  • Hello Junming,

    Please allow me a few days to look into your questions. There are layout guidelines in the datasheet that you can refer to in the meantime. 

    Thank you,

    Best Regards,

    Shruti

  • HI Shruti:

     I designed it according to the layout guide,So I don't have any new ways to solve this ESD problem.This project is very urgent. Could you please help me to see if there is any solution as soon as possible.

    Thank you,

    Best Regards,

    Junming!

  • Hello Junming,

    Can you please share pictures of your set up including cable? What kind of enclosure is the device in? Can you describe the ESD test that you are doing? The system level measures you can take are making sure that there is path of low resistance to ground where the voltage strike occurs during the test. 

    The 964 is not meant to be used with the internal reference clock. The accuracy of the internally generated FrameSync is directly dependent on the accuracy of the 25 MHz oscillator used as the reference clock. We recommend that you use the external clock. 

    Best Regards,

    Shruti

  • HI Shruti:

    Now I have some new problems.

    1.The serializer output from my device uses DS90UB927.I found ESD problems, the phenomenon is the same as DS90UB964,But my DS90UB927 is STP.

    For DS90UB927 and DS90UB964, I made a video in which I did the experiment.The following is my video. It can be seen that the input screen of the four cameras will be wrong, and the output screen will also be wrong.The input chip uses DS90UB964, and the output chip uses DS90UB927.

    Thank you,

    Best Regards,

    Junming!

  • Hello Juming,

    I am not sure what you mean by, "It can be seen that the input screen of the four cameras will be wrong, and the output screen will also be wrong.The input chip uses DS90UB964, and the output chip uses DS90UB927."

    927 is an IVI part and the 964 is an ADAS part.

    Can you please clarify your set up? Could you please provide a block diagram? I also don't quite fully understand form the video. Can you please share you replies for my pervious questions? It looks like you have metal encasing?

    Best Regards,

    Shruti

  • HI Shruti:

    This is my hardware block diagram.

    My screen shows the output of DS90UB927. The images of the four cameras are input to the CPU by DS90UB964. DS90UB964 sent from the picture through the CPU processing. The CPU transmits the processed picture to the screen through DS90UB927 for display.

    The current problem is that both 927 and 964 chips have problems under static electricity.

    Thank you,

    Best Regards,

    Junming!

  • Hello Junming, 

    Thank you for sharing the block diagram and clarifying. For ESD issues you should ensure you have good grounding at the connector, and if there are added external ESD diodes, good grounding to the GND plane. 

    Can you please share your schematics and layout so I can check a few things?

    A "pdf" file for the schematic and ".brd" file for the layout would be great.

    You can send them as a message to me on E2E.

    Best Regards,

    Shruti

  • HI Shruti:

    I have sent an email to you through Amelie Zheng. The email contains schematic and PCB. Help to see if there are any measures that can be improved!

    Thank you,

    Best Regards,

    Junming!

  • Hello Junming,

    when you zap the ESD, what is the rating? Can you try a smaller value? 

    Do you have the TVS diodes placed near the connector (not the device pins)? You can try grounding the metal shell separately. 

    Best,

    Shruti

  • HI Shruti:

    I have tried grounding the metal casing separately and not grounding the metal casing separately.That doesn't seem to change the outcome, right.

    "Do you have the TVS diodes placed near the connector (not the device pins)?"

    You can take a look at my PCB file and schematic file.Do you mean to add a TVS diodes near the connector?I'll use an ESD diodes to connect to a TVS diodes.Are there any suggestions for TVS diodes parameters?

    Do you have any suggestions for the FPD-link layout of our PCB files?

    Thank you,

    Best Regards,

    Junming!

  • Hello Junming,

    Can you please provide ".brd" file for your layout? It's more user friendly. 

    You can use a TVS diode for ESD protection. The ESD diodes on the PCB should be as close to the connector as possible. The diodes have to be low capacitance, like capacitance of 0.5pF and lower or less than 0.3pF if possible. The standoff/breakdown voltage should be able to withstand the PoC voltage.

    Best Regards,

    Shruti