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Digital Frequency/Phase Comparator (DFPC) - better than 4046 PH.C.II ?

Discussion in 'Electronic Design' started by Glenn, Jan 15, 2013.

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  1. Glenn

    Glenn Guest

    Some time ago I found this on the www:

    Atmel, Digital Frequency/Phase Comparator (DFPC):
    (with circuit schematic)

    Is this DFPC (using 4000 or 74HC series logic) better that the phase
    comparators used in e.g. 4046, 74HC7046, 74HC9046?

    4046 schematic on page 5:

    When was the DFPC invented? Is it free to the DFPC for any purpose?

  2. Am 15.01.2013 18:38, schrieb John Larkin:

    ....I'd like that PFD2, too! In SC-70 !!!
    The 9046 is said to be better, but I have not used it personally.
    The AD9901 is a nice alternative. It moves the deadband to the
    extremes of the phase range, where nobody is molested.

    I recently rewrote it in VHDL, but we decided to stay with
    a FLL, so it is not needed anymore.
    Maybe I'll test it just for fun in a corner of a small Coolrunner..

    regards, Gerhard
  3. Glenn

    Glenn Guest

    On 15/01/13 22.06, Gerhard Hoffmann wrote:

    Is there a very small cheap FPGA where a PFD2 can be implemented?

    The smallest I could find at digikey and cheapest ($10 ! ) had 64 pins.


    What about a universal 16/24/28/32square pin 74HC/74LVC/... FPGA - burn
    your own (a)sync counter/PFD2/PLL/NOR/NAND/NOT/LCD-driver/... - and of
    course more complicated things?


    It is even possible to buy single gates today - example:

    SN74AUC1G08DBVR - 74AUC1G08 - a dual input AND Gate:

  4. Am 16.01.2013 07:19, schrieb Glenn:

    Probably needs another SC-70 for the 1V8 core voltage.

  5. The '9046 is definitely better. I have used it in SONET retiming PLLs.

    For those not in the know, the logic in the PFD is the same as that in
    the '4046, but the output is different. Instead of the hard P pullup and
    N pulldown, there is a P pullup current source and an N pulldown current
    sink. The currents are matched to perhaps 1% (although this is not
    guaranteed in the datasheet).

    The '9046 output Z is alway high, unlike that of the '4046 which is
    modulated by the phase error.

  6. Guest

    a XC9536XL-10VQG44C at digikey is 1.18$ in ones

  7. Guest

    what would be the advantage of using diodes instead of just a tristate
    or two ?

  8. rickman

    rickman Guest

    How many FFs do you want? There are some very low power devices from
    Lattice that come in low pin count packages, but not so easy to use,
    small pitch BGAs as small as 36 pins, 2.5 mm sq. They are targeted to
    the mobile device market so they are pretty cheap, I think they are well
    under $5 in quantity. iCE40xxxx, 1.2 volt core

  9. o pere o

    o pere o Guest

    If I had to do it, I would use a 44-pin CPLD (no configuration hassles)
    in a PLCC package, such as Altera's EPM3064ALC44-10N for 1.78 EUR at
    Digikey. I gues this is the smallest beast.

  10. Guest

    if you look at the timing spec for a xilinx cmos output the numbers
    data-to-pad and tristate-to-pad is exactly the same, so whether you
    the data or the tristate pin the output transistor must be doing the

    you get the same "slam to the rail"
    you could do the same with two outputs and no diodes

    something like this:

    assign pc2_p = up ? 1'b1 : 1'bz;
    assign pc2_n = down ? 1'b0 : 1'bz;

  11. Guest

    with a single high-low-tristate output that would be impossible
    yes, of course if you do up and down at the same time they
    will fight each other but so will two push-pull outputs with
    diodes unless I missed how you'd connect them

  12. Guest

    I guess xilinx cmos outputs are also current controlled (ish)
    at least they are described that way, being programmable with
    2,4,6,8,12,16 or 24mA drive and fast or slow slew rate

  13. Guest

    I think the diodes are redundant if you made the two outputs push/
    tristate - pull/tristate
    and there would be diode voltage more for the resistors to set the
    is it really needed, wouldn't pwm/delta-sigma into the integrator work
    just as good?

    if it works for pll-mode it should work for non-pll mode, every thing
    is the same it is just what controls the pins that changes

  14. josephkk

    josephkk Guest

    Nice. For many things i am contemplating i am looking for something like
    an old 22v10. Just checked, they are still around, cool. It can do
    several PFD2s and replace several packages of tiny logic at the same time.

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