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adv7343 circuit questions

Hi ADI's

One of my customers is reviewing product development using the ADV7343.

RS170 (640 x 480,30fps), 4 channels of black and white video are used in Black Bar mode.
would like to implement the structure below.


 

1. Should the DAC1 ~ 3 be directly connected to the datasheet of the ADV7343 by BNC, and should the DAC4 ~ 6 be connected to the BNC using Amp?

2. Can I use ADA4432 as an amp when using DAC 4 ~ 6?

3. Should test pattern occur one by one when DAC1 ~ 4 occurs? Or can it happen at the same time?

Thank you

  • Hi,

     Generally ADV7343 operate in two mode for DAC configuration

      High drive mode:
       I.   Rset1 controls DAC 1,2,3 and 510 Ohm sets it to high drive mode
       II.  DACs 1,2,3 are in high drive mode and expect to see 37.5 Ohm load, this includes the 75 Ohm to ground and the 75 Ohm to ground for cable termination.    
       III. Pros: More noise immunity (better SNR)  Cons: More power consumption
     Low drive mode:
        I.   Rset2 controls DAC 4,5,6 and 4.12 KOhms sets it to low drive mode
        II.  DACs 4,5,6 are in low dirve mode and expect to see 300 Ohm load to ground.  The buffer/filter has 2x gain and drives into 75 Ohm series resistor and the 75 Ohm termination impedance.
        III. Pros: Lower power consumption  Cons: More prone to interference
    1. Should the DAC1 ~ 3 be directly connected to the datasheet of the ADV7343 by BNC, and should the DAC4 ~ 6 be connected to the BNC using Amp?
          Depend on the drive mode, you can group and configure the DAC.
    2. Can I use ADA4432 as an amp when using DAC 4 ~ 6?
           Yes,you can use.

    3. Should test pattern occur one by one when DAC1 ~ 4 occurs? Or can it happen at the same time?   
          Simultaneous SD and ED/HD input and output are supported.

    Note: The section 'VIDEO OUTPUT BUFFER AND OPTIONAL OUTPUT FILTER' shows the optional recommended filters and buffer.  This is with the DACs configured for low drive mode
    If you don't want to use a buffer or filter then the DACs need to be in a high drive mode to source the 75 Ohm cable.

    Thanks,

    Poornima