Now looking at making a new board, using the AD724 clocked in sync with the incoming video signal’s colourburst. This is looking like quite a challenge. The basic principle has been shown to work, but it requires a lot of ICs. Am considering using the AD8001 as the pixel switch as it has “excellent video characteristics” according to the datasheet, which also gives a reference circuit for exactly that. However it requires a dual +-5V supply and I am not sure what is the best way to provide this. More research needed. Could it be as simple as 2 +5V LDOs, with the positive rail of one and the negative rail of the other, becoming GND?
Am also wondering how much of the 550mA used by my existing design, is due to losses by the inefficient linear voltage regulators? If I changed them to switch-mode regulators, could I bring the power down to 300mA? And could I do this while keeping noise within acceptable limits? I will try to measure the actual current drawn by the video chips from the LDO regulators. To date I have only measured total current drawn from the 5V USB power supply which includes losses from the LDOs.
Weka OSD 