Question
I'm thinking about using ADV7180 video decoder in my application. My question
is if is possible to connect 27MHz clock oscillator to pin XTAL or I have to
use 28.6363MHz clock oscillator only. I know about existence of the EN28XTAL
bit - default is in log1, for log 0 there is 27MHz clock option. I'm not sure,
because of timing specification of the system clock in the datasheet. Q2: Is
that XTAL Pin 3.3V tolerant ?
Answer
Q1: No, the 27MHz will not work, the clock recommended for best performance is
the 28.63636 MHz clock.
In some earlier encoder devices a 27MHz crystal was used but this was changed
to 28.63636 to avoid intermodulation noise between the sampling clock and line
lock clock. For best performance we recommend the use of a 28.6363MHz crystal.
Q2: The Xtal inputs are protected to 1.8V PVDD supply internally, so the part
will operate with a 3.3V external clock, however we cannot recommend using a
3.3V oscillator for normal operation, since the ADV7180 datasheet specifies
1.8V only.