[time-nuts] 4046 replacement

[REEVES Paul]

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-bounces at 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 <wb6bnq at 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 at 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 at 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 at febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.