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DS90UB953A-Q1: ferrite beads on power

Part Number: DS90UB953A-Q1

Tool/software:

Team,

Valeo wants to get ride of ferrite beads. there are asking us to justify when they are absolutely necessary. I only found use of ferrite beads in PoC and in the 927 datasheet.

https://www.tij.co.jp/lit/ds/symlink/ds90ub927q-q1.pdf

what is our overall position about ferrite ?

why is it specifically mentioned in the 927 datasheet (see "8.2 Typical Application") ?

olivier

  • Hello Olivier,

    We are using FB in the Typical applications diagrams for almost all of our devices. For the UB953A you can find this in Figure 8-3, page 68.

    I can't tell you which one is more necessary and which not. We believe that all three FBs are necessary and recommended for multiple reasons, for example:

    - EMI Suppression
    - Improve Supply decoupling
    - Controlling parasitic oscillation
    - Reduce high-frequency coupling from and into the device.

    Also, during our testing and validation, we have used these components. If Valeo want to remove them, they must make sure their device/system works as expected and can fulfill all our specifications across all PVT.

  • Hamzeh,. thanks but those are for POC application (Figure 8-3, page 68), not applicable when the device is "normally" powered as opposed to see "8.2 Typical Application" of 927 ?

  • Olivier,

    I am not sure I understood what FB you mean. Can you please provide the schematic from the customer and highlight those FBs in it?

  • Hamzeh, sure. the 927 is the only one ( i found) with this suggestion:

    on some other datasheet you can find suggestion for ferrite in case you use power over coax, but I don't think this is what valeo is asking about : I hope they understand why ferrites coverign the various frequencies are required in case of PoC. hence my questions is more, how do we justify the need for ferrites outside of PoC similar to suggested application schematic of 927 which doesnt seem to involve Poc but regular power.

  • Olivier,

    As I said, almost all FPD-Link devices use these power-supply pins FB as I stated in my first reply.

    As you can see for example the UB953A. These FB are for power-supply pins not for PoC.

  • Hamzeh,

    Ok thanks, do we have test result showing with/without performance on any FPD device?

    thanks

  • Unfortunately not. We do all of our testing and validations with these FBs.

  • thanks, could be interesting to reassess and optimize this. Not sure Maxim recommends FB, but even if they do a finer understanding of what they actually bring could help : maybe a good topic for intern or NCG in rotation ?

  • Hamzeh,

    tougher than I expected, I guess maxim doesnt recommend ferrite...

    "

    I understand your points, but this is not a justification.

     

    Also, as you say, you are doing all your tests with ferrite beads, but how can you justify the necessity if you do not perform tests without the ferrite beads ?

     

    Today, there are solutions on the market without ferrite beads, and ferrite beads have an impact on the carbon footprint of our product.

     

    So, it is not possible anymore to use them without any justification, and we will start to include the ferrite beads in the price comparison. 

     

    Please push this topic TI internally.

    "

  • Olivier,

    As I said, FBs are just recommendations, not requirements. Hence, the customer can get rid of them, but they must make sure their device/system works as expected and can fulfill all our specifications across all PVT.

  • ok PVT ? what's the meaning of the acronym?

  • PVT is a term we use during qualifications and validations of the device. Which means Process - Voltage - Temperature

  • Hamzeh,

    I think it would still be interesting to perform a quick assessment on EVMs if we see any difference at all : if we dont it wont really prove anything, but valeo may feel more comfy not adding it to the FPD solution cost vs competition (and try and stop using FB in their design) . If we do see a difference, then that will be the justification valeo is asking for...

    what do you think ?

  • Hi Olivier,

    I think we clarified your questions on the call, hence closing.