Forums

Low Jitter 20MHz oscillator

Started by hbv March 1, 2013
On Sat, 2 Mar 2013 20:04:02 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

>On Mar 2, 6:20&#2013266080;pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My- >Web-Site.com> wrote: >> On Sun, 03 Mar 2013 00:15:03 +0100, Habib Bouaziz-Viallet >> >> <h.bouazizvial...@free.fr> wrote: >> >On 03/03/2013 00:09, langw...@fonz.dk wrote: >> >> A 74HCU04,an xtal, 2 caps, 2 resistors and you have a very nice >> >> oscillator >> >> >> -Lasse >> >> >Ahh ok a simple RC oscillator on 20MHz ! mmhhh ... i would not >> >experiment such a basic thing when stable, cheap and reliable integrated >> >oscillators exits for years with a jitter as low as 1ps. >> >> >Thank anyway, Habib. >> >> Habib, Your debut if off to a very shaky start. &#2013266080;Most of the world >> uses 74HCU04 as the core of their crystal oscillators. &#2013266080;And those >> two-pin ports on Microchip's uP's... guess what's inside ?:-) >> >> &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; &#2013266080; ...Jim Thompson
[snip]
> >Hi Jim, What's the advantage of the U version for xtal drive? > >Thanks, >George H.
The "U" stands for "unbuffered". A standard 74HC04 (no "U") inverter is actually 3 inverters in series, to scale up the power gain. The "U" version is just a single (2-transistor) inverter, so it's simply a transconductance device... in other words, an amplifier ;-) Most crystal oscillators use some variation of the 'HCU04 configuration. In more critical applications, AGC is applied to... guess what?... the 'HCU04 configuration... to make it a completely linear amplifier, with good spectral characteristics. My MC1648 (circa 1968) is a bipolar example of an AGC'd oscillator to get good spectral characteristics. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | 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.
On Friday, March 1, 2013 5:41:08 AM UTC-8, hbv wrote:
> Hi all, > > > > We need a low jitter clock generator ( 3v3 or 1v8 CMOS output single > > ended ), 20Mhz (+-few percent...) and most important a low jitter on > > this output (few ps). > > > > Any ideas are welcomed. Habib.
Jitter is a function of the phase noise profile. Set your jitter spec., calculate your jitter from the phase noise of your chosen oscillator. Then you don't need to argue with anybody. It's not difficult.
On Sun, 03 Mar 2013 10:01:34 +0100, Habib Bouaziz-Viallet
<h.bouazizviallet@free.fr> wrote:

>On 03/03/2013 04:34, John Larkin wrote: >> make sure it and the ADC have very quiet, >> well bypassed power >Ok my first plan was to power the analog card with a 3V6 battery. > >I realize that driving modern ADC clock input is not so trivial (like >LTC2203) >> >> the oscillator supply and the ADC >> logic supply are the same rail >> >Ok.
The LTC2203 has a single-ended clock input, which is OK if handled very carefully. It's better to use a clock and an ADC with differential PECL or LVDS levels; the edges are faster, and power supply and ground noise are much smaller hazards. We did a box that uses an LTC2242-12, a 12-bit ADC running at 250 MHz. The clock is AC-coupled differential, which makes it pretty much immune to low frequency and common-mode noise. https://dl.dropbox.com/u/53724080/Circuits/ESM/ESM_rev_B.jpg Often, maybe usually, picosecond jitter is caused by *low* frequency effects: power supply ripple, ground loops, switcher noise, cmos analog noise, temperature fluctuations, clock 1/f phase noise. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Habib Bouaziz-Viallet wrote:
> > On 03/03/2013 04:54, John Larkin wrote: > ? He's a redneck, and at the low end of that scale. > > Jim is a little bit condescendant with French guys like me but he must > not as an analog innovatOR and as a good wines amatOR. I guess he spent > too a long time in the cellar and returning here afterwards pissing on > my shoes. > > These old men are incorrigible!
You condem others, but have to ask for help. That piss on your shoes is your own.
On Sun, 03 Mar 2013 14:49:11 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

> >Habib Bouaziz-Viallet wrote: >> >> On 03/03/2013 04:54, John Larkin wrote: >> ? He's a redneck, and at the low end of that scale. >> >> Jim is a little bit condescendant with French guys like me but he must >> not as an analog innovatOR and as a good wines amatOR. I guess he spent >> too a long time in the cellar and returning here afterwards pissing on >> my shoes. >> >> These old men are incorrigible! > > > You condem others, but have to ask for help. That piss on your shoes >is your own.
Read Thompson's posts. Unprovoked insults and slurs. Not to mention mostly wrong. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On 03/03/2013 19:09, John Larkin wrote:
> We did a box that uses an LTC2242-12, a 12-bit ADC running at 250 MHz. The clock > is AC-coupled differential, which makes it pretty much immune to low frequency > and common-mode noise.
Yes surely the single ended input clock requires more attention by us (PCB stack up issues, Power supplies and signal integrity) thank you for pointing these topics and we have been some experience on that subjects.
> > https://dl.dropbox.com/u/53724080/Circuits/ESM/ESM_rev_B.jpg >
Seems to be such a thing approching what we plan to do. Great piece of electronics design.
> Often, maybe usually, picosecond jitter is caused by*low* frequency effects: > power supply ripple, ground loops, switcher noise, cmos analog noise, > temperature fluctuations, clock 1/f phase noise.
That is always the same guys, Spehro, you and a few others who are speaking about electronics designs down here. Recently someone tells me to not question anything about electronics and just let some guys like Jim Thompson the great guru analog innovaTOR pissing me off. What a pity ! Habib.
On Sun, 03 Mar 2013 23:16:26 +0100, Habib Bouaziz-Viallet
<h.bouazizviallet@free.fr> wrote:

>On 03/03/2013 19:09, John Larkin wrote: >> We did a box that uses an LTC2242-12, a 12-bit ADC running at 250 MHz. The clock >> is AC-coupled differential, which makes it pretty much immune to low frequency >> and common-mode noise. >Yes surely the single ended input clock requires more attention by us >(PCB stack up issues, Power supplies and signal integrity) thank you for >pointing these topics and we have been some experience on that subjects. >> >> https://dl.dropbox.com/u/53724080/Circuits/ESM/ESM_rev_B.jpg >> > >Seems to be such a thing approching what we plan to do. Great piece of >electronics design. > >> Often, maybe usually, picosecond jitter is caused by*low* frequency effects: >> power supply ripple, ground loops, switcher noise, cmos analog noise, >> temperature fluctuations, clock 1/f phase noise. > >That is always the same guys, Spehro, you and a few others who are >speaking about electronics designs down here. > >Recently someone tells me to not question anything about electronics and >just let some guys like Jim Thompson the great guru analog innovaTOR >pissing me off. > >What a pity ! > >Habib.
Jim Thompson a Master Circuit Designer; no less authority than Jim Thompson told us so. At 16 bits, clock jitter might be swamped by analog circuit noise. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Mar 3, 9:58=A0am, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My-
Web-Site.com> wrote:
> On Sat, 2 Mar 2013 20:04:02 -0800 (PST), George Herold > > > > > > > > <gher...@teachspin.com> wrote: > >On Mar 2, 6:20=A0pm, Jim Thompson <To-Email-Use-The-Envelope-I...@On-My- > >Web-Site.com> wrote: > >> On Sun, 03 Mar 2013 00:15:03 +0100, Habib Bouaziz-Viallet > > >> <h.bouazizvial...@free.fr> wrote: > >> >On 03/03/2013 00:09, langw...@fonz.dk wrote: > >> >> A 74HCU04,an xtal, 2 caps, 2 resistors and you have a very nice > >> >> oscillator > > >> >> -Lasse > > >> >Ahh ok a simple RC oscillator on 20MHz ! mmhhh ... i would not > >> >experiment such a basic thing when stable, cheap and reliable integra=
ted
> >> >oscillators exits for years with a jitter as low as 1ps. > > >> >Thank anyway, Habib. > > >> Habib, Your debut if off to a very shaky start. =A0Most of the world > >> uses 74HCU04 as the core of their crystal oscillators. =A0And those > >> two-pin ports on Microchip's uP's... guess what's inside ?:-) > > >> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 ...Jim Thompson
> [snip] > > >Hi Jim, What's the advantage of the U version for xtal drive? > > >Thanks, > >George H. > > The "U" stands for "unbuffered". > > A standard 74HC04 (no "U") inverter is actually 3 inverters in series, > to scale up the power gain. > > The "U" version is just a single (2-transistor) inverter, so it's > simply a transconductance device... in other words, an amplifier ;-) > > Most crystal oscillators use some variation of the 'HCU04 > configuration. =A0In more critical applications, AGC is applied to... > guess what?... the 'HCU04 configuration... to make it a completely > linear amplifier, with good spectral characteristics. > > My MC1648 (circa 1968) is a bipolar example of an AGC'd oscillator to > get good spectral characteristics. > > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 ...Jim Thompson
> -- > | James E.Thompson =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 | =A0 =A0mens =A0 =A0 |
> | Analog Innovations =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 | =A0 =A0 et =A0 =A0 =A0|
> | Analog/Mixed-Signal ASIC's and Discrete Systems =A0| =A0 =A0manus =A0 =
=A0|
> | Phoenix, Arizona =A085048 =A0 =A0Skype: Contacts Only =A0| =A0 =A0 =A0 =
=A0 =A0 =A0 |
> | Voice:(480)460-2350 =A0Fax: Available upon request | =A0Brass Rat =A0| > | E-mail Icon athttp://www.analog-innovations.com| =A0 =A01962 =A0 =A0 | > > I love to cook with wine. =A0 =A0 Sometimes I even put it in the food.- H=
ide quoted text -
> > - Show quoted text -
Got it, thanks Jim (and Tim) George H.
On Sun, 03 Mar 2013 14:49:11 -0500, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

> >Habib Bouaziz-Viallet wrote: >> >> On 03/03/2013 04:54, John Larkin wrote: >> ? He's a redneck, and at the low end of that scale. >> >> Jim is a little bit condescendant with French guys like me but he must >> not as an analog innovatOR and as a good wines amatOR. I guess he spent >> too a long time in the cellar and returning here afterwards pissing on >> my shoes. >> >> These old men are incorrigible! > > > You condem others, but have to ask for help. That piss on your shoes >is your own.
Aha! Habib is a dribbler ?>:-} ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | 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.
On Sunday, March 3, 2013 10:09:04 AM UTC-8, John Larkin wrote:
> On Sun, 03 Mar 2013 10:01:34 +0100, Habib Bouaziz-Viallet > > <h.bouazizviallet@free.fr> wrote: > > > > > Often, maybe usually, picosecond jitter is caused by *low* frequency effects: > > power supply ripple, ground loops, switcher noise, cmos analog noise, > > temperature fluctuations, clock 1/f phase noise. > >
you're talking about correlated system issues. goes without saying those components have to be dealt with. you don't want them setting your overall system spec. again, those contributions can be calculated. but ultimately timing systems specs starts with a master clock phase noise profile. in the case of downconverter all sources have to be considered. then it becomes obvious that spectral profiles can be shaped to maintain jitter, (time domain), specs.