CD4060 Xtl Osc. Circuit
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From: John Fields on 14 Mar 2010 13:17 On Sun, 14 Mar 2010 09:29:36 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: >On Sun, 14 Mar 2010 09:05:27 -0700, Joerg <invalid(a)invalid.invalid> >wrote: >>I am usually happy with around 1M. All it needs to do is to crank it >>over. Kaaaa-chum-pah ... POOF ... vrooooom. Unless I must start it >>really fast for some reason but that can require special kicker circuitry. > >Huh? You and I are talking two different resistors. I'm talking the >series drive resistor; you're talking the DC loop resistor. > >Which brings to mind... does the CD4060 have the DC loop resistor >built-in? It would appear not. --- No, but that's probably not a bad thing since you like 10M and I like 1M. One rather unfortunate thing, though, is that RESET stops the oscillator so you can't use RESET to do a divide-by-n unless you use an external clock. --- >And I should pay closer attention to details :-( The OP has 100K >there... needs to be 10-20Meg. --- Seems a little high ... I've always used 1 megohm JF
From: Jim Thompson on 14 Mar 2010 13:46 On Sun, 14 Mar 2010 12:17:10 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Sun, 14 Mar 2010 09:29:36 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote: > >>On Sun, 14 Mar 2010 09:05:27 -0700, Joerg <invalid(a)invalid.invalid> >>wrote: > >>>I am usually happy with around 1M. All it needs to do is to crank it >>>over. Kaaaa-chum-pah ... POOF ... vrooooom. Unless I must start it >>>really fast for some reason but that can require special kicker circuitry. >> >>Huh? You and I are talking two different resistors. I'm talking the >>series drive resistor; you're talking the DC loop resistor. >> >>Which brings to mind... does the CD4060 have the DC loop resistor >>built-in? It would appear not. > >--- >No, but that's probably not a bad thing since you like 10M and I like >1M. > >One rather unfortunate thing, though, is that RESET stops the oscillator >so you can't use RESET to do a divide-by-n unless you use an external >clock. >--- > >>And I should pay closer attention to details :-( The OP has 100K >>there... needs to be 10-20Meg. > >--- >Seems a little high ... I've always used 1 megohm > >JF My resistors are always on-chip :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Fred Bartoli on 14 Mar 2010 15:16 Jim Thompson a �crit : > On Sun, 14 Mar 2010 09:51:52 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > ... > > Mine are usually on-chip :-) > > ...Jim Thompson Really that small? -- Thanks, Fred.
From: ddd on 14 Mar 2010 15:51 Been some years since I commentd on crystal problems, the ancient UK phone line make it difficult and people seem to be getting more unplesant. To work out the suitability and margin for oscillation I recommend plotting the negative resistance of the circuit versus frequency. That is the negative resistace that appears across the crystal. At the oscillation frequency the negative resistance should exceed the crystal resistance by at least a factor of 2. The PI network oscillator can be shown to go from positive resistance up to a peak and then reduce over about 2 octaves. It is possible to select an overtone by careful selection of values.My recent discovery is that Switcher CAD can be induced to plot the aboce curves! Note that his is not exclusive to PI networks and I have a broadband DC coupled circuit that works from 1M to hundreds of megs without tuning and selects the overtone purely by resistance , not reliabley though as manufacturers of crystals are getting worse at making cheap consistent product. Currently Im rejecting 10% of bought in pagers as the crystal stops after a few months. This is due to the above and that crystals increase their "start up" resistance with time if not properly manufactured. Note crystal drive level is not the same as circuit activity and optimum activity can be inconsistent with adequate negative resistance. Nice to be back Doug Dwyer "Boris Mohar" <borism_void_(a)sympatico.ca> wrote in message news:e1spp590s16i3a3t91vehcsssc26lv1qqq(a)4ax.com... > On Sat, 13 Mar 2010 00:20:46 GMT, steveupton(a)gerber.com (Steve Upton) > wrote: > >>I have copied the CD4060 part of the CMOS synthesizer in the link >>below to the letter, but it does not work. I am using a 12VDC SLA for >>supply. It tries to start when I tease the caps, but then dies. >> >>I've spent hours tinkering to no avail. Can anyone see what is might >>be going amiss? Or can anyone please provide a similar circuit that >>works? >> >>http://www.redclifferadioclub.org.au/QRM/2006%2010%20-%20October%20QRM.pdf >> >>Steve Upton > > I don't see any local decoupling caps. > > -- > Boris --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Joerg on 14 Mar 2010 16:25
Jim Thompson wrote: > On Sun, 14 Mar 2010 09:51:52 -0700, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Sun, 14 Mar 2010 09:05:27 -0700, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Jim Thompson wrote: >> [...] >> >>>>> My rule of thumb, which seems to work with every inverter-style >>>>> crystal oscillator I've ever tried: Use capacitors as recommended by >>>>> the crystal specification... if it says 15pF, that means 30pF on EACH >>>>> end to ground. Then choose the resistor based on 45� phase shift with >>>>> the first capacitor (at the crystal frequency). >>>>> >>>> I am usually happy with around 1M. All it needs to do is to crank it >>>> over. Kaaaa-chum-pah ... POOF ... vrooooom. Unless I must start it >>>> really fast for some reason but that can require special kicker circuitry. >>> Huh? You and I are talking two different resistors. I'm talking the >>> series drive resistor; you're talking the DC loop resistor. >>> >> Ok, different thing. Mostly you can get away without although that's not >> always the nice way of doing things. >> >> >>> Which brings to mind... does the CD4060 have the DC loop resistor >>> built-in? It would appear not. >>> >> AFAIR not. >> >> >>> And I should pay closer attention to details :-( The OP has 100K >>> there... needs to be 10-20Meg. >>> >> I usually go for 1M. > > CD series stuff doesn't have a lot of gm. But 1Meg is good for > something like 74HCU04. > For the CD4060 they recommend even higher values, page 3: http://www.fairchildsemi.com/ds/CD%2FCD4060BC.pdf > DO NOT USE buffered inverters for crystal oscillators! > Depends on the frequency but generally yes, don't use those if you can avoid it. >> 10M may not work outdoors when humidity is high and >> some condensation occurs. > > Mine are usually on-chip :-) > Yup, a poly resistor is nice. But you can't put crystals on the chip :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |