Hi Donald, I've just had this problem - the 'signal' input (p14) to the phase detectors is a 'bodge' linear amplifier built around standard CMOS stages and it doesn’t work right. A resistor around a CMOS inverter was a good old recipe to get a 'linear' amplifier stage but this design appears to have a voltage variable resistor of sorts and it gives very strange results. It is fine if used as a CMOS level i/p stage but its use as an ac coupled low level i/p is problematic and may need additional loading. Manufacturer's documentation is scarce and I have only seen one reference to the internal design of this stage. There's quite a bit about it in several places on the net.
Regards, Paul Reeves G8GJA -----Original Message----- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of donald collie Sent: 18 April 2018 10:40 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] 4046 replacement Thankyou Attila. I remember reading a book on PLL theory, recently,writen by a very knowledgable fellow, but I didn`t think to make a copy of his critique of the 4046. I recall that the nub of it was that the 4046 isn`t suitable for some applications because of a design flaw. Perhaps somebody in this group could explain further. Thankyou Bill, for the datasheet on the 74HCT9046, and your comments Cheers!..............................................................................Don jnr ZL4GX <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> Virus-free. www.avg.com <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Wed, Apr 18, 2018 at 8:28 PM, wb6bnq <wb6...@cox.net> wrote: > Hi Donald, > > You could consider the NXP 74HCT9046A as a replacement. It is an > improved version of 4046. However, you do need to study the spec > sheet as it is a bit different, but in a good way. > > I have included an attached PDF of the spec sheet, if it makes through > the mail list server. > > Bill....WB6BNQ > > > donald collie wrote: > > I have 4 frequency synthesiser projects, each using HEF4046BCN`s, but > have >> recently read that this CMOS IC has a design flaw. What would be a >> better chip to retrofit? I`m thinking perhaps a HEF74HC4046AN [that`s >> if it doesn`t have the same bug], or a 74HC7046AN - which is similar. >> Both these chips are more-or-less pin compatable TIA for any >> advice!..................................................... >> ..................................................Don >> >> <http://www.avg.com/email-signature?utm_medium=email&utm_ >> source=link&utm_campaign=sig-email&utm_content=webmail> >> Virus-free. >> www.avg.com >> <http://www.avg.com/email-signature?utm_medium=email&utm_ >> source=link&utm_campaign=sig-email&utm_content=webmail> >> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to >> https://www.febo.com/cgi-bin/m ailman/listinfo/time-nuts and follow >> the instructions there. >> >> >> > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to > https://www.febo.com/cgi-bin/ mailman/listinfo/time-nuts and follow > the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.