[time-nuts] 74HCT9046A Max. Operating Frequency

wb6bnq wb6bnq at cox.net
Thu Apr 24 07:18:05 EDT 2014


Hello Samuel,

Well, I just got done designing and building the very same thing.  If I 
recall correctly it is the same as the HC4046 which is 4 MHz.  The 9046 
VCO will only go up to 20 MHz absolute maximum.  So you will need an 
external oscillator and dividers.

Bill....WB6BNQ

sg sg wrote:

>Hi,
>
>I'm about to implement a PLL for a 24.576 MHz VCXO using the phase-frequency detector (PC2) of the NXP 74HCT9046A. From the datasheet (www.nxp.com/documents/data_sheet/74HCT9046A.pdf) it is not clear to me what the maximum operating frequency for this phase detector is--from the enable and disable times (page 20 and figure 19) I presume 24.576 MHz is too much.
>
>So I probably need to add dividers at the inputs. Can someone advise me on the choice of division ratio?
>
>Thanks for your time,
>Samuel
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