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[ADV7482] Analog Component input Question.

Hi,

I have a question about analog component (YPbPr) input for ADV7482.
I summarized the questions to an attached file "ADV7482_Component_Input_Question.xlsx".
Please refer it.

Thank you!
Best regards.
Tamu

XLSX

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  • Hi Tamu San,

          Please find the below comment,

    When signals have different amplitude (Y:1000mV, PbPr:700mV) input to ADV7482 via same resistor divider network (24ohm and 51ohm), does it cause any problem?                    
    Does the customer have to equal  all amplitude of the YPbPr? (Does he have to equal them to all 1000mV or all 700mV etc.?)  

              I beleive no, It does cause any problem as long as the input range doesn't exceed upto 1.47 V p-p.

    Note:  The purpose of the resistor divider is to approximately half the inputted video signal voltage to the ADV748x. This prevents clipping and makes the ADV748x robust to variations in input voltages. The gain blocks within the ADV748xcompensates for the halving of the input voltage. 

    Note that resistor divider also supplies the 75 Ohm end termination that is needed for some applications.

    However the resistor divider network can be omitted if the input video voltage is:

    • Stable
    • Well controlled
    • Less than 1V peak-to-peak
    • If end termination of 75 Ohms is not needed

    Note that the 100nF AC coupling capacitor is vital to the correct operation of the ADV748x and cannot be omitted. The purpose of this capacitor is to remove the DC bias of the inputted video signal. The internal clamping circuitry of the ADV748x restores this DC value.

    Thanks,

    Poornima

  • Hi Poornima san,

    Thank you for your reply.

    What I'm worried about is whether the color on the display can be seen normally or not
    when signals have different amplitude (Y:1000mVpk-pk, PbPr:700mVpk-pk) input to ADV7482 via same resistor divider network (24ohm and 51ohm).

    The ADV748x Hardware Manual says as follows:


    This says "Luma Gain => Dependent on horizontal sync depth" and "Chroma Gain => Taken from luma path" on "YPrPb".
    YPbPr has three independent signals.
    So when the signals have different amplitude (Y:1000mVpk-pk, PbPr:700mVpk-pk), is there any possibility that the color on the display can not be seen normally?
    (because "Chroma Gain" is set from the luma (Y) path.)

    For example, the ADV748x script file includes as follows:
    ##04 Analog input YPrPb##
    :04-01 Analog YPrPb to MIPI TX-B CSI 1-Lane - Autodetect YPrPb In, Ain 1,2,3 - MIPI Out:

    Does the customer have any problem by using this script even if the component signals have different amplitude (Y:1000mVpk-pk, PbPr:700mVpk-pk)?
    AGC (Auto gain control) is used in this script. (Manual gain control is not included in this script.)
    Doesn't he have to use Manual gain control?

    As I mentioned on the attached file, the "Y" is 1000mVp-p including 300mVp-p as the sync.

    So I think it's no problem because the luma data is 700mVp-p(except sync) and this is same to PrPb's amplitude.
    But just in case, please let me ask the above question.

    Thank you!
    Best regards.
    Tamu

  • Hi Tamu San,

           I beleive, It doesn't cause any problem because 300mVp-p is sync but its not a luma data.

           Please check and let us know, if in case any issue then will check solution for that.

    Thanks,

    Poornima

  • Hi Poornima san,

    Thank you for your reply.

    >Please check and let us know, if in case any issue then will check solution for that.
    =>I'm sorry. I can't understand what you mean.. (I'm so sorry for my poor English..)

    My customer is going to make their system and board using ADV7482.
    So we have not seen any problem yet.
    But he wants to know whether it (Y:1000mVpk-pk, PbPr:700mVpk-pk input) is no problem or not.
    So he asks it to us.

    If it's no problem, I will tell so to the customer.
    Is this OK?

    Thank you!
    Best regards.
    Tamu

  • Hi Tamu San,

            I beleive, It doesn't cause any problem.

            If any issue occurred from customer end , then we will check on that.

    Thanks,

    Poornima

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