"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:1ufsh.68665$wP1.36056@newssvr14.news.prodigy.net...
Genome wrote:
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
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Genome wrote:
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:v8ash.2570$O02.2066@newssvr11.news.prodigy.net...
Ok, guys, another case where I have to ditch the uC idea and go
semi-discrete. Need a couple long timers so I am looking at the old
CD4060, hoping to find some in TSSOP stock.
For 5V it states the frequency as 23kHz +/-10%. But the usual formula
is f=1/(2.2*Rx*Cx) and that comes to about 45kHz. I can't imagine these
things to have more than a few ten pF in internal capacitances so this
doesn't compute. Look at the 4th page (page 3-161):
http://focus.ti.com/lit/ds/symlink/cd4060b.pdf
Any ideas why?
--
Regards, Joerg
http://www.analogconsultants.com
I know you might not like NXP..... but, for me that was quite painless.
Oh, I like them. What I don't like is their marketing "effort" and IMHO
their web site is crummy. Their specsmanship was always superb though.
http://www.standardics.nxp.com/products/hef/pdf/hef4060b.pdf
Page 3-160) Figure 12) on the TI Dirty Sheet shows your equation for the
'oscillator' frequency.
Page 5) Figure 4) on the Philips/NXP Data Sheet gives a similar
equation. They also give other useful information........ I like Philips
and Siemens for Data Sheets....
Anyway,
The 'Logic' diagram on the Philips Data Sheet, Page 3) Figure 3) might
make more sense. Notice that there are four flop flips before you get to
O3. Flop Flip 1 divides the 'oscillator' frequency by two before the
rest of the stuff sees it.
One has to be really, really careful with that stuff. For example Moto/ON
often calls the first output Q4 while others call it Q3. That can really
throw people a curve when they discover that after the layout is done. We
used to have an "anger pad" for such situations. It hung on a wall and
read: In case of an upcoming temper trantrum take one sheet, crumple and
throw into a corner.
The TI Dirty Sheet is referring to a Clock Signal after Flop Flip 1.
Fair enough, the Philips Data Sheet might not specifically make that
point but the TI/Harris logic diagram hides it deeper.
Of course if I knew fuck about logic I would have been able to work it
out from the TI Dirty Sheet. But I don't.......
However, having looked at the two.... the TI Dirty Shit might show Flop
Flip 1 connected as a Toggle (JK with inverted inputs which could be a
D-type) before the rest of the counters get to see it.
They are basically all used as deviders feeding each other. Not the most
modern concept but for a slow timer it's often good enough.
--
Regards, Joerg
http://www.analogconsultants.com
Oh, alright then.
You asked..... the difference between about 45KHz and about 23KHz is
about a factor of two. It's quite possible that 2 is a digital divide by
two so..........
Ah, that's what you meant. Could, of course, be but what puzzled me was
the mention of both on the same datasheet. And they mentioned the
oscillator (sans dividers).
You absolute old patronising bastard you!
Your job interviews must last at least four hours whilst you blither on
about the good old days and a few terminal 'war stories'. Then, having
bored yourself, you'll forget my name as you ask your secretary to dial
me a taxi.
Actually, they could last an hour but I asked the people about their
stories. Mine I told later after I hired them

))
Assuming I get through that load of shit and get the job you might just
give me a broken chair and back order a customised bercostat for delivery
about the time your Ronny James manages to lock you up a cupboard so they
can sort out the power supply pins on an LM324.
Your design reviews will be three hours of nodding at your extreme
ability to focus on where to place potentiostat1 on the PCB with a
screaming desire to get out, ignore your input and get the job sorted.
Then you'll probably visit three times a day to ask if any of the
resistors are a slight shade of blue because something went wrong when
you used blue resistors in 1965.
Nah, that was ten years later and what happened was that RF turned a
capacitor from white ceramic into green glass. It was amazing.
So, dinner time and then I'll pour us a cold one...
--
Regards, Joerg
http://www.analogconsultants.com
OK. So where did I go wrong?