[time-nuts] crunching numbers from XOR phase detector

[Azelio Boriani]

You're right there are 3 phase detectors in the 4046: RS and JK flip-flops
and and XOR gate.

On Wed, Jan 4, 2012 at 6:21 PM, Chris Albertson
<albertson.chris at gmail.com>wrote:

> On Wed, Jan 4, 2012 at 12:58 AM, Hal Murray <hmurray at megapathdsl.net>
> wrote:
>
> >
> > Neat.  Thanks for sharing.
> >
> > With a XOR, you can't tell which input is higher frequency.  I think you
> > can
> > fix that with a second XOR and a delay line.
>
>
> I think you can build a PFD or Phase Frequency Detector with three or four
> flip flops.  This avoid using the delay line and works over a wide range.
>
> If I'm not mistaken there is a PFD inside the 74HC4046.   It uses flip
> flops.  Be sure to look at the 74HC type not the cd4046.   The 75hc type
> works up to 18MHz.
>
>
> Chris Albertson
> Redondo Beach, California
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