XO controlled 480Hz Oscillator
in [Design]
|
Prev: The UT804 bench multimeter
Next: Small genset
From: JosephKK on 6 Feb 2010 22:27 On Sat, 06 Feb 2010 14:10:28 -0600, John Fields <jfields(a)austininstruments.com> wrote: >On Fri, 05 Feb 2010 22:13:58 -0500, Spehro Pefhany ><speffSNIP(a)interlogDOTyou.knowwhat> wrote: > >>On Fri, 05 Feb 2010 17:48:45 -0800, the renowned >>"JosephKK"<quiettechblue(a)yahoo.com> wrote: >> >>>On Fri, 05 Feb 2010 12:18:06 -0600, John Fields <jfields(a)austininstruments.com> wrote: >>> >>>>On Wed, 03 Feb 2010 22:35:43 -0500, ehsjr <ehsjr(a)nospamverizon.net> >>>>wrote: >>>> >>>>>Use Q13 to divide by 8192. >>>> >>>> Qn DIV BY >>>>-----|--------- >>>> Q0 2 >>>> Q1 4 >>>> Q2 8 >>>> Q3 16 >>>> Q4 32 >>>> Q5 64 >>>> Q6 128 >>>> Q7 256 >>>> Q8 512 >>>> Q9 1024 >>>> Q10 2048 >>>> Q11 4096 >>>> Q12 8192 >>>> Q13 16384 >>>> >>>> :-) >>>> >>>> >>>>JF >>> >>>I suspect that some datasheets list the outputs as Q1 through Q14. >> >> Function of pin #3 >>Fairchild Q14 >>NXP Q13 >>ON Q14 >>ST Q14 >>TI QN > >--- >I suspect you're right. > >I got my data from the Philips 1996 CMOS data book, but going back to >the RCA bible, it's listed as Q14. > >Thanks for the reality check. :-) > >JF I hope that Speff agrees with me, "De nada".
From: Paul Keinanen on 10 Feb 2010 02:44 On Tue, 09 Feb 2010 18:01:44 -0500, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >But the counter >timebase might not be that *accurate*. ~4MHz crystals are typically >accurate to +/-30-100ppm. 100ppm is 50 msec error in about 8 minutes, >just for comparison. 100 pm might apply to some cheap microprocessor crystals, but for decades (before frequency synthesizers) , channel crystals were made for radio telephones to within a few ppm. A 100 ppm crystal would have caused the transmission on the wrong channel, a slightly smaller error would cause bad audio distortion, since the signal would be partially outside the receiver de modulator bandwidth. When ordering a frequency for a specific frequency, specify also the load capacitance or specify the frequency slightly (a few dozen ppm) above the desired frequency and pull it down to the desired frequency with a parallel capacitor. Pulling upwards is harder with a series inductance. Overtone crystals (typically above 20 MHz) have a more limited pulling range.
From: Spehro Pefhany on 10 Feb 2010 09:11 On Wed, 10 Feb 2010 09:44:26 +0200, the renowned Paul Keinanen <keinanen(a)sci.fi> wrote: >On Tue, 09 Feb 2010 18:01:44 -0500, Spehro Pefhany ><speffSNIP(a)interlogDOTyou.knowwhat> wrote: > >>But the counter >>timebase might not be that *accurate*. ~4MHz crystals are typically >>accurate to +/-30-100ppm. 100ppm is 50 msec error in about 8 minutes, >>just for comparison. > >100 pm might apply to some cheap microprocessor crystals, but for >decades (before frequency synthesizers) , channel crystals were made >for radio telephones to within a few ppm. A 100 ppm crystal would have >caused the transmission on the wrong channel, a slightly smaller error >would cause bad audio distortion, since the signal would be partially >outside the receiver de modulator bandwidth. > >When ordering a frequency for a specific frequency, specify also the >load capacitance or specify the frequency slightly (a few dozen ppm) >above the desired frequency and pull it down to the desired frequency >with a parallel capacitor. Pulling upwards is harder with a series >inductance. Or if he really needs ppm-level accuracy/stability or better, replace the crystal with a TCXO or VCTCXO (or even OCXO if warm-up time is not important). Eg. http://www.ecsxtal.com/store/pdf/vc_txo_35sm.pdf or http://www.abracon.com/Precisiontiming/AOCJY.pdf Specs are important, because the 4060 apparently won't work with off-the-shelf frequencies, wheras the PIC or some equivalant combination of HCMOS could. >Overtone crystals (typically above 20 MHz) have a more limited pulling >range. Related to the inverse of the square of the overtone, so 1/9 range for a 3rd overtone. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
From: Chris on 10 Feb 2010 10:52 On Feb 10, 6:11 am, Spehro Pefhany <speffS...(a)interlogDOTyou.knowwhat> wrote: > On Wed, 10 Feb 2010 09:44:26 +0200, the renowned Paul Keinanen > > > > <keina...(a)sci.fi> wrote: > >On Tue, 09 Feb 2010 18:01:44 -0500, Spehro Pefhany > ><speffS...(a)interlogDOTyou.knowwhat> wrote: > > >>But the counter > >>timebase might not be that *accurate*. ~4MHz crystals are typically > >>accurate to +/-30-100ppm. 100ppm is 50 msec error in about 8 minutes, > >>just for comparison. > > >100 pm might apply to some cheap microprocessor crystals, but for > >decades (before frequency synthesizers) , channel crystals were made > >for radio telephones to within a few ppm. A 100 ppm crystal would have > >caused the transmission on the wrong channel, a slightly smaller error > >would cause bad audio distortion, since the signal would be partially > >outside the receiver de modulator bandwidth. > > >When ordering a frequency for a specific frequency, specify also the > >load capacitance or specify the frequency slightly (a few dozen ppm) > >above the desired frequency and pull it down to the desired frequency > >with a parallel capacitor. Pulling upwards is harder with a series > >inductance. > > Or if he really needs ppm-level accuracy/stability or better, replace > the crystal with a TCXO or VCTCXO (or even OCXO if warm-up time is not > important). > > Eg.http://www.ecsxtal.com/store/pdf/vc_txo_35sm.pdf > > or http://www.abracon.com/Precisiontiming/AOCJY.pdf > > Specs are important, because the 4060 apparently won't work with > off-the-shelf frequencies, wheras the PIC or some equivalant > combination of HCMOS could. > > >Overtone crystals (typically above 20 MHz) have a more limited pulling > >range. > > Related to the inverse of the square of the overtone, so 1/9 range for > a 3rd overtone. > > Best regards, > Spehro Pefhany > -- > "it's the network..." "The Journey is the reward" > sp...(a)interlog.com Info for manufacturers:http://www.trexon.com > Embedded software/hardware/analog Info for designers: http://www.speff.com This is the actual crystal I ordered from digikey: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=X975-ND If I get the thing dialed in, the 30ppm is tolerable for my application. I will try 25pF fixed capacitor for the PI network part of the circuit. If I am paranoid should I still figure a value to limit the current so that @ 12V the max power is ~2mw? Am I running into a greater chance that I will not be driving it enough to oscillate? Or is the minimum power so far below the max power limit that it does not matter? I will use a 2Meg resistor for the foldback. Maybe a 25pF trimmer in parallel will let me dial the freq right in. The specified crystal frequency is what I need. I am not trying to shift it off the package frequency. I just want to put some variability in so that I can compensate for stray capacitance after I have mounted it in the tape deck. Thanks Guys, Chris Maness
From: Spehro Pefhany on 10 Feb 2010 11:49
On Wed, 10 Feb 2010 07:52:52 -0800 (PST), Chris <christopher.maness(a)gmail.com> wrote: >On Feb 10, 6:11�am, Spehro Pefhany <speffS...(a)interlogDOTyou.knowwhat> >wrote: >> On Wed, 10 Feb 2010 09:44:26 +0200, the renowned Paul Keinanen >> >> >> >> <keina...(a)sci.fi> wrote: >> >On Tue, 09 Feb 2010 18:01:44 -0500, Spehro Pefhany >> ><speffS...(a)interlogDOTyou.knowwhat> wrote: >> >> >>But the counter >> >>timebase might not be that *accurate*. ~4MHz crystals are typically >> >>accurate to +/-30-100ppm. 100ppm is 50 msec error in about 8 minutes, >> >>just for comparison. >> >> >100 pm might apply to some cheap microprocessor crystals, but for >> >decades (before frequency synthesizers) , channel crystals were made >> >for radio telephones to within a few ppm. A 100 ppm crystal would have >> >caused the transmission on the wrong channel, a slightly smaller error >> >would cause bad audio distortion, since the signal would be partially >> >outside the receiver de modulator bandwidth. >> >> >When ordering a frequency for a specific frequency, specify also the >> >load capacitance or specify the frequency slightly (a few dozen ppm) >> >above the desired frequency and pull it down to the desired frequency >> >with a parallel capacitor. Pulling upwards is harder with a series >> >inductance. >> >> Or if he really needs ppm-level accuracy/stability or better, replace >> the crystal with a TCXO or VCTCXO (or even OCXO if warm-up time is not >> important). >> >> Eg.http://www.ecsxtal.com/store/pdf/vc_txo_35sm.pdf >> >> or �http://www.abracon.com/Precisiontiming/AOCJY.pdf >> >> Specs are important, because the 4060 apparently won't work with >> off-the-shelf frequencies, wheras the PIC or some equivalant >> combination of HCMOS could. >> >> >Overtone crystals (typically above 20 MHz) have a more limited pulling >> >range. >> >> Related to the inverse of the square of the overtone, so 1/9 range for >> a 3rd overtone. >> >> Best regards, >> Spehro Pefhany >> -- >> "it's the network..." � � � � � � � � � � � � �"The Journey is the reward" >> sp...(a)interlog.com � � � � � � Info for manufacturers:http://www.trexon.com >> Embedded software/hardware/analog �Info for designers: �http://www.speff.com > >This is the actual crystal I ordered from digikey: > >http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=X975-ND > >If I get the thing dialed in, the 30ppm is tolerable for my >application. I will try 25pF fixed capacitor for the PI network part >of the circuit. If I am paranoid should I still figure a value to >limit the current so that @ 12V the max power is ~2mw? Yes, particularly if you care much about drift. This particular xtal is rated at 1mW maximum. >Am I running >into a greater chance that I will not be driving it enough to >oscillate? Yes. You could empirically increase it until it doesn't start then go down by a fairly large safety margin (maybe 3:1). Or work it out from the transconductance of the oscillator amplifier (I think NXP specifies typical values on their HC datasheet). http://www.freescale.com/files/microcontrollers/doc/app_note/AN1783.pdf > Or is the minimum power so far below the max power limit >that it does not matter? I will use a 2Meg resistor for the >foldback. DC feedback = bias. > Maybe a 25pF trimmer in parallel will let me dial the freq >right in. The specified crystal frequency is what I need. I am not >trying to shift it off the package frequency. I just want to put some >variability in so that I can compensate for stray capacitance after I >have mounted it in the tape deck. > >Thanks Guys, >Chris Maness |