Interfacing of 74ALVC divider chain to ADF4350 output (yet another low jitter sine-to-logic thread ; ) )
Hello,
Trying to make low-PN fine tuning step synth for experiments in HF
range from the parts I have on hand. Looks like the best I can do is
to add extra dividers to chinese ADF4350 board from eBay that was used
in the past and now is collecting dust on the shelf.
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?
--
Sincerely,
Yuri, UA3ATQ/KI7XJ mailto:yuri@ostry.ru
On Sun, 30 Jul 2017 23:52:50 +0300
Yuri Ostry yuri@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
Hello,
Thank you for your reply!
Monday, July 31, 2017, 0:25:19, Attila Kinali wrote:
A> Alternatively, use something like an SY89874 as first divider
A> stage to get down to a more managable frequency range, then
A> continue with your ALVC dividers.
I think it will be easier (faster and cheaper) to get ADF4351 chip
and replace it on that board, getting two more divider stages inside synth
chip. Pinout is the same, if memory serve me correctly. AD is easier
to get here compared to exotic Micrel clock buffer.
Looks like there will be no such "quick and dirty" way with 4350.
--
Best regards,
Yuri mailto:yuri@ostry.ru
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.
Bruce
On 31 July 2017 at 09:25 Attila Kinali <attila@kinali.ch> wrote:
On Sun, 30 Jul 2017 23:52:50 +0300
Yuri Ostry <yuri@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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