AD9517-1 frequency range conflict

The data sheets are a little conflicting. I would like to use this part to drive an AD9739 via the ADCLK914 at 2.4GHz. I would also like to generate a 1.2GHz LVDS/analog clock to a national ADC12D1800. The AD9517 would generate the clocks from a 10MHz reference or an external 2.4GHz input. One part of the data sheet shows a 2.95GHz max LVPECL output, 800MHz LVDS. Power curves provided suggest that this will be of sufficient amplitude to drive the ADCLK914. However, other parts of the datasheet say that the PECL output is only up to 1.6GHz and that you must use the divide by 2 to maintain this output frequency.

My application would need to output the 2.4GHz direcly on one differential channel and half that frequency on another. The source of this clock would either be the direct internal clock or a directly coupled external clock of 2.4GHz. Will this part work with sufficient amplitude for each? The National part needs a typical diff input of .6V for the clock.

Will this work?



  • 0
    •  Analog Employees 
    on Dec 23, 2011 1:21 AM over 9 years ago

    Hi Dan,

    I apologize for the confusion. We limit the max output frequency in the datasheet so that we can meet the target output amplitude specs. The driver will toggle faster, but the waveform will look more sinusoidal.

    The AD9517 will drive the ADCLK914 just fine at 2.4 GHz, but you may need to keep them relatively close together as many circuit board dielectrics are lossy at 2.4 GHz. Definitely use LVPECL mode. In fact, I'd use use the AD9518 and use all LVPECL, as LVDS performance isn't super above 700 MHz. You can AC-couple and adjust the output amplitude of the AD9517/18 LVPECL drivers if you need to. If the National part is expecting LVDS amplitudes at 1.2 GHz, the AD9517 LVPECL driver will be able to deliver that just fine. If you really want to use the AD9517 LVDS driver, keep the trace length short, and be ready to use the increased LVDS amplitude settings of the AD9517.

    For the 2.4 GHz signal, use the Y-termination scheme shown in Figure 72 of the datasheet.

    The other 1.6 GHz max spec for the drivers has to do with the channel divider that does the /1 to /32. Its max input frequency is 1.6 GHz, but you can do up to 2.95 GHz in VCO direct mode.

    -Paul Kern

  • Hi Paul,

    Thanks for the info. It looks like this will be a good part for my apps. I will probably go to the 9518 like you suggest.