Hello,
I have two questions about threshold of color kill function (CKILLTHR) of ADV7282A.
There is "Table 47. CKILLTHR[2:0] Function" on ADV7280A/ADV7281A/ADV7282A Device Manual, UG-1176 as follows:
Question 1:
Could you tell me what the percentages in this table mean?
What does the 100% mean?
For example, in case of NTSC, I think that the 100% means 285.6mV.
(In case of NTSC, 100IRE = 714mV, color burst amplitude = 40IRE = 714mV x 0.4 = 285.6mV. So I think the 100% = 285.6mV.)
Is this my understanding correct?
Question 2:
The default setting(010) indicates "Kill at <2.5%" in the "Table 47. CKILLTHR[2:0] Function".
Is this correct?
In the datasheet, "VIDEO SPECIFICATIONS" indicates that the Minimum of "Color Burst Range" = "5%".
And you said as follows:
ez.analog.com/.../373671
Your comment : "Note : ADV728x may not work for poor video signals. If the color burst is below that percentage of the standard's value then the color will be killed, this will happen due to weak signal.
If the color subcarrier is below 14.275mVpp,then the ADV7280 will not be able to lock to the color subcarrier and it will output a black and white image."
I think the 14.275mVpp is based on 5% of 285.6mV.
However, the datasheet says "5%" and the device manual says the default value is "2.5%", which doesn't make sense.
About this, I think that the "Kill at <2.5%" in the Device Manual, UG-1176 means "plus-minus" 2.5% (= peak-to-peak 5%).
If the "Table 47. CKILLTHR[2:0] Function" on UG-1176 indicates "plus-minus" percentage value (The peak-to-peak amplitude value is double this value), it make sense.
Is this my understanding correct?
Thank you!
Best regards.
Tamu