Hi,
For ADCLK925, input differenctial range is: 0.2Vpp to 3.4Vpp.
In dBm (50 ohm system), that is from -10dBm to +15dBm.
To verify, I have checked by bench test.
The ADCLK925 can go as high as +17dBm. The AD9915's performance degrades once you input +18dBm at ADCLK925. However, I would suggest you limit your input to +15dBm only to guarantee performance on ADCLK925.
For lower limit, you can go as low as -10dBm.
Hope this helps.
-Sittie