CD4046 Question
in [Design]
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From: Phil Hobbs on 23 Feb 2010 18:21 On 2/23/2010 5:51 PM, Ban wrote: > Phil Hobbs wrote: > snip> >> With phase-frequency detectors it's pretty easy--the output goes to >> the rail when it's out of lock, so a window comparator works well. >> >> The 4046 also has the "phase pulses" output that (very roughly) tells >> you what the phase error is, so you can filter that and use a >> comparator. I don't think that works as well as the window >> comparator method. >> >> With an XOR gate or diode mixer PD, you need a second PD plus a 90 >> degree phase shift. One excellent method is to use a divide-by-4 >> Johnson counter (aka walking ring). Run the main PD off one output >> and the lock detector off the other. >> > > Don't write about something you do not know well Phil, that makes "brutta > figura" > > everything is wrong, > In lock is lets say within +/-30� Phaseangle. The phase comparator2 puts > out pulses according to how far apart are the edges of the input freqency > and the oszillator frequency. the control voltage of the VCO are these > pulses smoothed out by the loop filter. When it is in lock these pulses are > short, so you can drive a cap through a resistor and with a Schmitt you can > create a threshold switch to indicate this fact. It is only with an absent > input, that the oscillator drifts to the lowest frequency. And only if you > use phase comparator 2. > With PC1 the center frequency is put out with absent input signal. But "not > in lock" and absent input are two different conditions. > > ciao Ban > > > > Ban, I said "phase-frequency detector". An XOR is not a phase-frequency detector. With an XOR or diode-bridge PD, the only reliable method I know of to indicate lock is to use another PD with a 90 degree phase shift, and look for a high level at its output. As an aside, I've been designing high performance PLLs since I was a kid astronomer, circa 1981--my first real job was designing all the time and frequency-keeping for the first direct broadcast telecom system, the Spacetel from AEL Microtel. Talk about being chucked in the deep end--I'd never seen a PLL in my life, and wound up having to invent a new kind of fractional-N synthesis method to get the job done. That's where I first learned to do the algebra carefully before designing stuff. Otherwise I'd have been toast. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Ban on 23 Feb 2010 18:34 Phil Hobbs wrote: > On 2/23/2010 5:51 PM, Ban wrote: >> Phil Hobbs wrote: >> snip> >>> With phase-frequency detectors it's pretty easy--the output goes to >>> the rail when it's out of lock, so a window comparator works well. >>> >>> The 4046 also has the "phase pulses" output that (very roughly) >>> tells you what the phase error is, so you can filter that and use a >>> comparator. I don't think that works as well as the window >>> comparator method. >>> >>> With an XOR gate or diode mixer PD, you need a second PD plus a 90 >>> degree phase shift. One excellent method is to use a divide-by-4 >>> Johnson counter (aka walking ring). Run the main PD off one output >>> and the lock detector off the other. >>> >> >> Don't write about something you do not know well Phil, that makes >> "brutta figura" >> >> everything is wrong, >> In lock is lets say within +/-30� Phaseangle. The phase >> comparator2 puts out pulses according to how far apart are the edges >> of the input freqency and the oszillator frequency. the control >> voltage of the VCO are these pulses smoothed out by the loop filter. >> When it is in lock these pulses are short, so you can drive a cap >> through a resistor and with a Schmitt you can create a threshold >> switch to indicate this fact. It is only with an absent input, that >> the oscillator drifts to the lowest frequency. And only if you use >> phase comparator 2. With PC1 the center frequency is put out with >> absent input signal. But "not in lock" and absent input are two >> different conditions. ciao Ban >> >> >> >> > Ban, > > I said "phase-frequency detector". An XOR is not a phase-frequency > detector. With an XOR or diode-bridge PD, the only reliable method I > know of to indicate lock is to use another PD with a 90 degree phase > shift, and look for a high level at its output. > > As an aside, I've been designing high performance PLLs since I was a > kid astronomer, circa 1981--my first real job was designing all the > time and frequency-keeping for the first direct broadcast telecom > system, the Spacetel from AEL Microtel. Talk about being chucked in > the deep end--I'd never seen a PLL in my life, and wound up having to > invent a new kind of fractional-N synthesis method to get the job > done. > That's where I first learned to do the algebra carefully before > designing stuff. Otherwise I'd have been toast. > Its about the 4046 or equivalent here not your high performance stuff and who says PD2 in a 4046 is an XOR? ciao Ban
From: Phil Hobbs on 23 Feb 2010 18:50 On 2/23/2010 6:34 PM, Ban wrote: > Phil Hobbs wrote: >> On 2/23/2010 5:51 PM, Ban wrote: >>> Phil Hobbs wrote: >>> snip> >>>> With phase-frequency detectors it's pretty easy--the output goes to >>>> the rail when it's out of lock, so a window comparator works well. >>>> >>>> The 4046 also has the "phase pulses" output that (very roughly) >>>> tells you what the phase error is, so you can filter that and use a >>>> comparator. I don't think that works as well as the window >>>> comparator method. >>>> >>>> With an XOR gate or diode mixer PD, you need a second PD plus a 90 >>>> degree phase shift. One excellent method is to use a divide-by-4 >>>> Johnson counter (aka walking ring). Run the main PD off one output >>>> and the lock detector off the other. >>>> >>> >>> Don't write about something you do not know well Phil, that makes >>> "brutta figura" >>> >>> everything is wrong, >>> In lock is lets say within +/-30� Phaseangle. The phase >>> comparator2 puts out pulses according to how far apart are the edges >>> of the input freqency and the oszillator frequency. the control >>> voltage of the VCO are these pulses smoothed out by the loop filter. >>> When it is in lock these pulses are short, so you can drive a cap >>> through a resistor and with a Schmitt you can create a threshold >>> switch to indicate this fact. It is only with an absent input, that >>> the oscillator drifts to the lowest frequency. And only if you use >>> phase comparator 2. With PC1 the center frequency is put out with >>> absent input signal. But "not in lock" and absent input are two >>> different conditions. ciao Ban >>> >>> >>> >>> >> Ban, >> >> I said "phase-frequency detector". An XOR is not a phase-frequency >> detector. With an XOR or diode-bridge PD, the only reliable method I >> know of to indicate lock is to use another PD with a 90 degree phase >> shift, and look for a high level at its output. >> >> As an aside, I've been designing high performance PLLs since I was a >> kid astronomer, circa 1981--my first real job was designing all the >> time and frequency-keeping for the first direct broadcast telecom >> system, the Spacetel from AEL Microtel. Talk about being chucked in >> the deep end--I'd never seen a PLL in my life, and wound up having to >> invent a new kind of fractional-N synthesis method to get the job >> done. >> That's where I first learned to do the algebra carefully before >> designing stuff. Otherwise I'd have been toast. >> > Its about the 4046 or equivalent here not your high performance stuff and > who says PD2 in a 4046 is an XOR? > > ciao Ban > > Ban, What's your beef exactly? You're the one quoting the PD labels. I've been using 4046s for 30 years. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Jim Thompson on 23 Feb 2010 19:29 On Tue, 23 Feb 2010 18:12:26 -0500, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >On 2/23/2010 5:15 PM, Jim Thompson wrote: >> On Tue, 23 Feb 2010 17:04:26 -0500, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> [snip] >>> >>> With phase-frequency detectors it's pretty easy--the output goes to the >>> rail when it's out of lock, so a window comparator works well. >> >> What output is that? > >The filtered PD output, e.g. at the VCO input. When there's a frequency >error, the 4046's output goes between tristate and one logic level, so >the integrated output rails and sits there. That's one of the good >things about it--I've often used it as a lock detector for PLLs whose >main phase detector was a diode bridge. (My fave is the Mini-Circuits >MPD-1.) So it's not instantaneous? > >> >>> >>> The 4046 also has the "phase pulses" output that (very roughly) tells >>> you what the phase error is, so you can filter that and use a >>> comparator. I don't think that works as well as the window comparator >>> method. >> >> Measuring something that is exactly zero width is a wee bit tricky. > >But you don't need to. You can decide how big a phase variance you're >willing to tolerate, and set the threshold accordingly. Thought is >required. "Thought is required." ??? Crikey! You trying to out snot Larkin ?:-) > >> >>> >>> With an XOR gate or diode mixer PD, you need a second PD plus a 90 >>> degree phase shift. One excellent method is to use a divide-by-4 >>> Johnson counter (aka walking ring). Run the main PD off one output and >>> the lock detector off the other. >>> >>> Cheers >>> >>> Phil Hobbs >> >> What you mean is a "close-to-lock" detector is "easy" ?:-) >> >> ...Jim Thompson > >No. A PLL is in lock when the frequency error is zero, and the variance >of the phase error is bounded. You obviously haven't spent enough time >in low SNR situations. ;) > > >Cheers > >Phil Hobbs I haven't used a PLL for signal detection since the '60's... just synthesizers since. Knowing that a synthesizer is truly locked and still not "wobbling" is critical to know prior to turning on a transmitter. ...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 | I love to cook with wine. Sometimes I even put it in the food.
From: Jim Thompson on 23 Feb 2010 19:31
On Wed, 24 Feb 2010 00:34:25 +0100, "Ban" <bansuri(a)web.de> wrote: >Phil Hobbs wrote: >> On 2/23/2010 5:51 PM, Ban wrote: >>> Phil Hobbs wrote: >>> snip> >>>> With phase-frequency detectors it's pretty easy--the output goes to >>>> the rail when it's out of lock, so a window comparator works well. >>>> >>>> The 4046 also has the "phase pulses" output that (very roughly) >>>> tells you what the phase error is, so you can filter that and use a >>>> comparator. I don't think that works as well as the window >>>> comparator method. >>>> >>>> With an XOR gate or diode mixer PD, you need a second PD plus a 90 >>>> degree phase shift. One excellent method is to use a divide-by-4 >>>> Johnson counter (aka walking ring). Run the main PD off one output >>>> and the lock detector off the other. >>>> >>> >>> Don't write about something you do not know well Phil, that makes >>> "brutta figura" >>> >>> everything is wrong, >>> In lock is lets say within +/-30� Phaseangle. The phase >>> comparator2 puts out pulses according to how far apart are the edges >>> of the input freqency and the oszillator frequency. the control >>> voltage of the VCO are these pulses smoothed out by the loop filter. >>> When it is in lock these pulses are short, so you can drive a cap >>> through a resistor and with a Schmitt you can create a threshold >>> switch to indicate this fact. It is only with an absent input, that >>> the oscillator drifts to the lowest frequency. And only if you use >>> phase comparator 2. With PC1 the center frequency is put out with >>> absent input signal. But "not in lock" and absent input are two >>> different conditions. ciao Ban >>> >>> >>> >>> >> Ban, >> >> I said "phase-frequency detector". An XOR is not a phase-frequency >> detector. With an XOR or diode-bridge PD, the only reliable method I >> know of to indicate lock is to use another PD with a 90 degree phase >> shift, and look for a high level at its output. >> >> As an aside, I've been designing high performance PLLs since I was a >> kid astronomer, circa 1981--my first real job was designing all the >> time and frequency-keeping for the first direct broadcast telecom >> system, the Spacetel from AEL Microtel. Talk about being chucked in >> the deep end--I'd never seen a PLL in my life, and wound up having to >> invent a new kind of fractional-N synthesis method to get the job >> done. >> That's where I first learned to do the algebra carefully before >> designing stuff. Otherwise I'd have been toast. >> >Its about the 4046 or equivalent here not your high performance stuff and >who says PD2 in a 4046 is an XOR? > >ciao Ban > It's shown that way on the data sheet ?? ...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 | I love to cook with wine. Sometimes I even put it in the food. |