What is the duty cycle of REFx_IN @ AD9549?
It is 45(min), 55(max) % ?
Or varaety duty cycle is avalable ?
For example, Hi 10% Low 90% ?
The AD9549, just like all of our parts, has a spec of min pulse with high/low, and for the AD9549 it's 620ps. As long as the input clock is high (or low) for a minimum of 620ps, you're fine.
However, this means that the duty cycle requirements become more stringent as the input frequency goes up. For example, in order to meet the 620ps spec at the maximum specified input frequency of 750 MHz, you need a duty cycle in the 46.5% to 53.5% range.
However, the allowable duty cycle at lower input frequencies is obviously much more relaxed.