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DS90UB960-Q1: PoC Clarifications required.

HARI T O1
Expert 1675 points

Part Number: DS90UB960-Q1

Dear Team,

Below is the PoC circuit.

My questions are given below.

  1. Why 3 ferrite beads (FB1,FB2,FB3) are connected in series.
  2. How to design these ferrite beads
  3. Why there is a resistor connected in parallel with inductor(R1 & L1)

Regards

HARI

  • 0
    TI__Mastermind 27551 points

    Hi Hari,

    Thanks for reaching out with this question. 

    1. Why 3 ferrite beads (FB1,FB2,FB3) are connected in series.
      1. These ferrite beads are included here to separate the power carried over the coax cable from the high speed FC & BC. 
    2. How to design these ferrite beads
      1. Please see the application note referenced below regarding guidance on how to design a PoC network.
    3. Why there is a resistor connected in parallel with inductor(R1 & L1)
      1. The resistor which is connected in parallel with the inductor is used to modify the impedance characteristics of the L1 inductor across frequency. By introducing a resistor in parallel with the inductor the impedance profile is spread over a wider frequency with a lower peak impedance.

    For technical details regarding the usage of PoC, you may find it helpful to consult this PoC application note which discusses the usage of PoC with FPD-Link ADAS devices.

    Best,

    Thomas

  • 0 in reply to Thomas Bejin
    Expert 1675 points

    Hi Thomas,

    Thank you for your reply.

    I go through the material you suggested. It provides a general overview of PoC.

    Does not contain any design calculations.

    If you see the below image you can see that the inductor value is 10uH,how they arrived 10uH why not 1uH or 100uH.

    I would like to see the math behind the Bead selection ,Inductor selection and the parallel resistor selection.

    Regards

    HARI

  • +1 in reply to HARI T O1
    TI__Mastermind 27551 points

    Hi Hari,

    With regards to the specific details of network design such as inductor and resistor selection, it would likely be helpful to reach out to a passive component vendor such as Murata, Coilcraft, or TDK to help with these questions. We collaborate with these vendors in the development of the networks which we recommend for our devices.

    Best,

    Thomas