Getting pixel data from the ADV7611 into a DAC

Sirs:

I am using an ADV7611 HDMI receiver and the output bus is connected to a ADV7125 DAC.  Unfortunately the ADV7125 will not interface with the differential IQ lines to my ADL5375 modulator.

May I substitute an AD9785 or a AD9776A for the ADV7125?  I want to get my pixel data from the ADV7611 into a DAC that will allow me to connect to the IQ lines of my modulator.

  • Hi,

    We have just forwarded your question to the part specialist.

    Best Regards,

    Jeyasudha.M

  • It might be possible but you those parts will not insert the blanking and sync pulses into the analog output.  The best bet might be to post process the ADV7125 outputs to match the ADL5375 inputs. 

    Also the ADV7611 would need to ouptut YCbCr 4:2:2

    I am not exactly sure of your application so it is hard to make any real recommendations as to the best solution.

  • In addition to the last post:

    the differential signals from the ADV7125 DAC I believe are 180 deg out of phase. The IQ modulator ADL5375 requires that the signals be 90 degrees between the I & Q inputs - so therefore the differential outputs of the DAC should be made to be in 90 degrees phase: this is one of the post processing that is referred in the last post by Guenter. You would also need to terminate the analogue outputs either IOR or IOB to ground using a suitable resistor since the ADL5375 requires 2 differential I and Q inputs. You would still need to hook up filters before the modulator to remove the Nyquist images.

    Maybe you need to come up with a proper block diagram of your application-as this will help in understanding fully what you intend to carry out.

  • Depending on your application, could you perhaps use a mixer to upconvert the RGB data?

    If you have to use the ADL5375, as edo mentioned, the I and Q inputs need to be in quadrature phase - 90 degrees apart, to get a single-side band output. Also, please keep in mind that the required common mode voltages on the ADL5375 is 0.5V for the ADL5375-05 and 1.5V for the ADL5375-15. Looking at the ADV7125 datasheet, it looks like the full scale current output can be adjusted by Rset. If Rset is set to 20mA, then it will set 0.5V with 50 ohm on source termination on ADV7125. Then it can interface to ADL5375-05 directly.

    Please refer to "DAC MODULATOR INTERFACING" SECTION on page 24 of ADL5375 Datasheet.

  • I am going to insert a picture of what we are trying to accomplish.  Thank you.

    !