[ADV739x] "SD chroma filter" register (Address:0x80, bit[7:5])

Hi,

I have a question about "SD chroma filter" register (Address:0x80, bit[7:5]) of ADV739x.
According to the datasheet table 64 - table 78, when we want ADV739x to output NTSC, I think you recommend "SD chroma filter" register = 000 (1.3 MHz chroma filter enabled).

Question:
What kind of bad influence is assumed when "SD chroma filter" register is 111 (3.0 MHz chroma filter enabled) for NTSC output?

Background:
My customer uses ADV7390 for their project. And they have been evaluating ADV7390 now.
When "SD chroma filter" is 000 (1.3 MHz chroma filter enabled), they can see blurred color between Green and Magenta on color bar like below:

When "SD chroma filter" is 111 (3.0 MHz chroma filter enabled), they say they can see it improves.
They want to know what kind of bad effects occurs when "SD chroma filter" is 111 (3.0 MHz chroma filter enabled) because you recommend "SD chroma filter" register = 000 (1.3 MHz chroma filter enabled).

Thank you!
Best regards.
Tamu

  • 0
    •  Analog Employees 
    on Dec 30, 2020 11:19 AM 2 months ago

    Hi Tamu-San,

           In our evaluation board we don't face any color issue when configuring the SD chroma filter as 1.3MHZ. If possible could you please share your configuration?

           But it doesn't create any bad effect when SD chroma filter as changed to '111'(3.0MHZ). Have you tried with other sources ?

           Please make sure your power supplies are clean and very stable.
          Also if any impedance mis-match can also cause an color issue,So expert suggested a simple tool here that can give you a first pass estimate of what the trace impedance is for various board stack ups and trace widths. Please crosscheck with your board with impedence calculator

           PCB Trace Impedance Calculator 

    Do you have any DAC filters on the output? Filter is optional but recommended for best results.  The best filter really depends on your format. Please refer Page69, it give several options for SD, ED and HD formats.

    Thanks,

    Poornima