[time-nuts] 74HCT9046A Max. Operating Frequency

Magnus Danielson magnus at rubidium.dyndns.org
Thu Apr 24 19:29:27 EDT 2014



On 04/24/2014 10:41 AM, 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?

24,576 MHz is 128x192 kHz which makes essentially any divide by 2^N chip 
capable of the frequency a target. Is your reference signal also 24,576 
MHz or some other frequency?

Cheers,
Magnus



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