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AD9548 - Qu's on the stable source input.

Question asked by tomphelps on Oct 3, 2011
Latest reply on Oct 6, 2011 by tomphelps

Hi all,


I'm currently working on the AD9548 using the Analogue Devices evaluation board. We are integrating it into an existing system which has a 10MHz sinewave source and we were hoping to utilise this as the AD9548 stable source.


I have read in the data sheet that when using a sine source the frequency ideally should be above 20MHz, will a signification degradation in performance be seen if we remain with our 10MHz source? As a note i am using the clock doubler within the clock multiplier.


In addition to the above the data sheet mentions the ideal source to be  AC-coupled/1Vp-p/CMOS. With a sinewave of 10MHz what size capacitor would be best for the ac-coupling? In addition to this should the sinewave be 1Vp-p before or after the blocking capacitor(ac-coupled)? With a 1Vp-p sinewave signal before my blocking cap I'm seeing a 500mVp-p signal after that is dc offset by ~1V at the AD9548 source pin. I'm only using SYSCLKP and not SYSCLKN which is isolated from SYSCLKP and has had a decoupling capacitor to ground added at R30 as suggested.



Hope my questions are clear and look forward to any replies.


Thanks in advance.