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ADV739x: Video Encoder outout circuit

Thread Summary

The user inquires about using an AC coupling capacitor in series with the DAC output of the ADV7390. The final answer confirms that series capacitors can be used to block DC current and remove DC offset, but emphasizes the need to place external filter and buffer components close to the ADV7390 to minimize noise and trace capacitance effects. The user's understanding is correct: AC coupling is possible, but the receiving side must be evaluated, and ADI does not guarantee this configuration as it is outside the datasheet specifications.
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Category: Hardware
Product Number: ADV739x

Hi,all.
we have question of ADV739x DAC output circuit.
Is it possible to use a circuit configuration like the following diagram, where a capacitor is inserted in series with the DAC output of the ADV7390?

best regards
AimPoint.

Parents
  • Hi,

      As per expert comment, We can use series capacitors to completely block the DC current flow through the signal path (The Cap is a DC blocking cap).

     The series capacitors block this DC offset and the input pin will bias the signal that is acceptable to the part.
     Also we can remove DC-Offset with a high-pass filter.

     Kindly refer here at (+) ADV7393: DC Offset on Output of DAC1 - Q&A - Video - EngineerZone (analog.com)

     Note: External filter and buffer components connected to the DAC outputs should be placed as close as possible to the ADV7390/ ADV7391/ADV7392/ADV7393 to minimize the possibility of noise pickup from neighboring circuitry and to minimize the effect of trace capacitance on output bandwidth. 

    Thanks,

    Poornima

  • Hi,Poornima

    Thank you for your response. Let me check a little more.

    Is the following understanding correct?

    a) There is no problem in installing an AC coupling capacitor to the ADV7390 DAC output on the ADV7390 board as a stand-alone unit.

    b) However, it is necessary to check/evaluate whether the receiving side (video decoder side) can receive/display the signal normally.

    c) ADI cannot guarantee the operation of an AC coupling capacitor on the ADV7390 DAC output on the ADV7390 board, because it is outside the ADV7390 datasheet specifications.

    If the above understanding is correct, we will reply to the customer based on it.

    best regards
    AimPoint.

Reply
  • Hi,Poornima

    Thank you for your response. Let me check a little more.

    Is the following understanding correct?

    a) There is no problem in installing an AC coupling capacitor to the ADV7390 DAC output on the ADV7390 board as a stand-alone unit.

    b) However, it is necessary to check/evaluate whether the receiving side (video decoder side) can receive/display the signal normally.

    c) ADI cannot guarantee the operation of an AC coupling capacitor on the ADV7390 DAC output on the ADV7390 board, because it is outside the ADV7390 datasheet specifications.

    If the above understanding is correct, we will reply to the customer based on it.

    best regards
    AimPoint.

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