[time-nuts] Interfacing of 74ALVC divider chain to ADF4350 output (yet another low jitter sine-to-logic thread ; ) )

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Jul 30 18:46:58 EDT 2017

Use an LTC6957 the CMOS output of which has its PN specified at frequencies up to 300MHz.

Virtually any discrete circuit replacement with similar performance will require a higher voltage and dissipate more power.


>     On 31 July 2017 at 09:25 Attila Kinali <attila at kinali.ch> wrote:
>     On Sun, 30 Jul 2017 23:52:50 +0300
>     Yuri Ostry <yuri at ostry.ru> wrote:
>         > > 
> >         But interfacing of 74ALVC flip-flop input to a ADF output in a 160-260 MHz
> >         range is not so easy question for me, especially taking low jitter
> >         requirements into account. Maybe someone can share tested working solution that
> >         will not add too much noise and will be more or less stable with
> >         temperature variations?
> > 
> >     > 
>     CMOS signals get a bit iffy when going over 100MHz. You will probably
>     have to build your own board for the divider. I don't think it would
>     be reliable without it. As for interfacing the ADF4350 output, you will
>     need to use the differential output to cross the board-to-board gap.
>     On the divider board use a differential pair to convert the signal
>     to proper CMOS levels. You can use the one in the TADD2 or TICC
>     as an example how to do it. Make sure the f_t of the transistors
>     is high enough and that you give them enough current to work with.
>     Keep all wires on the divider board short and remove all planes
>     underneath the circuit, safe for the (closed) ground plane on the
>     bottom layer, in order to minimize stray capacitance.
>     Alternatively, use something like an SY89874 as first divider
>     stage to get down to a more managable frequency range, then
>     continue with your ALVC dividers.
>     Attila Kinali
>     --
>     You know, the very powerful and the very stupid have one thing in common.
>     They don't alters their views to fit the facts, they alter the facts to
>     fit the views, which can be uncomfortable if you happen to be one of the
>     facts that needs altering. -- The Doctor
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