AD725
Production
The AD725 is a very low cost general purpose RGB to NTSC/
PAL encoder that converts red, green and blue color component
signals into their corresponding...
Datasheet
AD725 on Analog.com
Hello
I found that AD725 requires TTL levels for 4FSC but I could not find NTSC crystal which is 5v! so I thought will a 3.3v crystal work fine??
as seen in my picture, the circuit is simple. I have a SP3T switch (or any mechanism) that feeds 0v for choosing PAL, 3,3v for NTSC or just another throw for auto detection (circuit not shown here). this circuit needs more tuning but you get the idea.
I really need very easy and stable solution which doesn't require tuning...
so can AD725 accept 3.3v crystal signals?
what crystals do you suggest? I need some part numbers please since finding them is very hard now.
thanks
The 14.318MHz oscillators are fine.
I would not use a MEMs oscillator for 17.73MHz oscillator. These oscillators are used to generate the color burst and MEMs devices in general have too much jitter. They might work for limited temp ranges. You can order 17.73MHz oscillators direct from the manufacturers, it's just that they aren't stocked by digikey. You can also search findparts.com and trustedparts.com for stock.
FYI, Since the AD725 was released 25 years ago, crystal manufacturers have stop making 5V oscillators, the best we can source is 3.3V oscillators now, therefore we need level translators.
I've attached the user guide with schematic for the AD725. You'll notice it uses a mechanical switch to select oscillators but you can use a silicon switch also.
The 14.318MHz oscillators are fine.
I would not use a MEMs oscillator for 17.73MHz oscillator. These oscillators are used to generate the color burst and MEMs devices in general have too much jitter. They might work for limited temp ranges. You can order 17.73MHz oscillators direct from the manufacturers, it's just that they aren't stocked by digikey. You can also search findparts.com and trustedparts.com for stock.
FYI, Since the AD725 was released 25 years ago, crystal manufacturers have stop making 5V oscillators, the best we can source is 3.3V oscillators now, therefore we need level translators.
I've attached the user guide with schematic for the AD725. You'll notice it uses a mechanical switch to select oscillators but you can use a silicon switch also.
