[time-nuts] 4046 variations (was EPE GPS....)

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Sun Sep 27 21:56:26 UTC 2009

On 9/27/09 1:54 PM, "Magnus Danielson" <magnus at rubidium.dyndns.org> wrote:

> Javier Herrero wrote:
>> Yes, I'm also familiarized with space qualified EEE components, and
>> lately I hear the word "heritage" more frequently that I would like ;)
>> The only design I've made for aircraft electronics was for a commercial
>> aircraft application, and the components selection was a lot less
>> restringent than for space (I think also that the system for which I
>> worked was also not classified as very critical), so perhaps the
>> decision to use a 4046 at its limit was driven by that heritage reasons,
>> and that really there was not too much better things around :) The
>> venerable 4046 has been around for quite a long time...
> Surely would other alternatives to the 4046 be possible even within the
> scope of heritage components? DBM and active mixers should be available
> and useable. The CCO (it's actually current controlled with a V/I
> conversion) could also be replaced. Logical gates can also be used to
> replace the phase-detector. Not as handy, but the aspect of the 4046
> causing trouble could be circumvented if needed. Another aspect is to
> improve its performance by design.
> But maybe I misinterprent the heritage aspect her in that it is designs
> rather than components that is inherited?

Design AND component...

Easy to claim heritage if all you do is change a resistor or a capacitor.
Tougher to claim if you change the active components, particularly if it's
functionally different (e.g. Substituting a 2n3904 for a 2n2222 isn't a huge
deal.. Changing a NPN to a PNP and reversing bias, or using FETs instead of
bipolars.. That would be a big deal)

Keeping those 30 year old databooks is important.. (as we tell the folks who
say: "why do you need all that shelf space.. Surely those datasheets are
available on line")..  1980s design, modified in 1990s, using parts first
available in 1970s, launched in 2000s, gets to Saturn in 2010s, has inflight

Oddly, the 4000 series CMOS are still heavily used.  Back in the 70s and
80s, I hated those parts because they were ESD sensitive (compared to
straight or LS ttl), but by today's standards, they're rock solid, have huge
junctions, work at any supply voltage.


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