Hi, i need help on finding a crystal for my application .. the requirements are: drive level : max 500mW CL : 20pF f : 25Mhz I have looked every where, and nobody has a crystal that meets those two requirements when i find a oscillator with f.x 25Mhz and CL=20pF it dosent have enough drive level, and if i find one with CL=20pF and ok drive level than it is not made in 25Mhz .. ARGH !! :p Anyone have any suggestions ?
Crystal supplier
Started by ●February 19, 2008
Reply by ●February 19, 20082008-02-19
On Tue, 19 Feb 2008 05:58:49 -0800, kislo wrote:> Hi, i need help on finding a crystal for my application .. the > requirements are: > drive level : max 500mW > CL : 20pF > f : 25Mhz > > I have looked every where, and nobody has a crystal that meets those two > requirements when i find a oscillator with f.x 25Mhz and CL=20pF it > dosent have enough drive level, and if i find one with CL=20pF and ok > drive level than it is not made in 25Mhz .. ARGH !! :p > > Anyone have any suggestions ?In the US, International Crystal Manufacturing and JAN Crystals both make custom-cut crystals in small quantities. If I'm not mistaken most manufacturers will custom cut them for you in sufficiently large quantities. I don't know, but I assume that even if you're off shore you should be able to find a manufacturer who'll get you prototype quantities. Finally, are you sure you need just exactly those specifications? Unless your oscillator has the capacitors built in you should be able to use a crystal with specifications that are close. Certainly if you find one that requires _more_ capacitance you can load it down easily enough, and in extremis you may be able to use one that calls for less capacitance with a suitable series inductor. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Reply by ●February 19, 20082008-02-19
In comp.arch.embedded, Tim Wescott <tim@seemywebsite.com> wrote:> > in extremis you may be able to use one that calls for less capacitance > with a suitable series inductor.Shouldn't that be a series _capacitor_ ? -- Stef (remove caps, dashes and .invalid from e-mail address to reply by mail) "Computers in the future may weigh no more than 1.5 tons." (Popular Mechanics, 1949)
Reply by ●February 19, 20082008-02-19
On Tue, 19 Feb 2008 17:27:37 +0100, Stef wrote:> In comp.arch.embedded, > Tim Wescott <tim@seemywebsite.com> wrote: >> >> in extremis you may be able to use one that calls for less capacitance >> with a suitable series inductor. > > Shouldn't that be a series _capacitor_ ?Uh, uh, uh -- yes. I always make good decisions the second time around, which is why it's a good thing my eyes weren't good enough for me to become a fighter pilot. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
Reply by ●February 19, 20082008-02-19
"kislo" ...> Hi, i need help on finding a crystal for my application .. the > requirements are: > drive level : max 500mW > CL : 20pF > f : 25MhzAre you sure you need that drive level? What are you trying to build, a sonoluminiscence set-up? :-) Or did you misinterpret uW (micro-Watt) for mW (milli-Watt), a factor of 1000 off? Arie de Muijnck
Reply by ●February 19, 20082008-02-19
Would you define the term "drive level" as you are using it here? Hul kislo <kislo02@student.sdu.dk> wrote:> Hi, i need help on finding a crystal for my application .. the > requirements are: > drive level : max 500mW > CL : 20pF > f : 25Mhz> I have looked every where, and nobody has a crystal that meets those > two requirements when i find a oscillator with f.x 25Mhz and CL=20pF > it dosent have enough drive level, and if i find one with CL=20pF and > ok drive level than it is not made in 25Mhz .. ARGH !! :p> Anyone have any suggestions ?
Reply by ●February 20, 20082008-02-20
On Tue, 19 Feb 2008 05:58:49 -0800 (PST), kislo <kislo02@student.sdu.dk> wrote:>Hi, i need help on finding a crystal for my application .. the >requirements are: > drive level : max 500mW > CL : 20pF > f : 25Mhz > >I have looked every where, and nobody has a crystal that meets those >two requirements when i find a oscillator with f.x 25Mhz and CL=20pF >it dosent have enough drive level, and if i find one with CL=20pF and >ok drive level than it is not made in 25Mhz .. ARGH !! :p > >Anyone have any suggestions ?The only situation in which the crystal drive level might be an issue is in some ancient single stage tube transmitters (prior to 1960's). For any embedded application, the crystal power limit should not be an issue. For frequencies above 20 MHz you might need a circuit suitable for an overtone crystal. Paul
Reply by ●February 20, 20082008-02-20
On Wed, 20 Feb 2008 11:06:20 +0200, Paul Keinanen wrote:> On Tue, 19 Feb 2008 05:58:49 -0800 (PST), kislo <kislo02@student.sdu.dk> > wrote: > >>Hi, i need help on finding a crystal for my application .. the >>requirements are: >> drive level : max 500mW >> CL : 20pF >> f : 25Mhz >> >>I have looked every where, and nobody has a crystal that meets those two >>requirements when i find a oscillator with f.x 25Mhz and CL=20pF it >>dosent have enough drive level, and if i find one with CL=20pF and ok >>drive level than it is not made in 25Mhz .. ARGH !! :p >> >>Anyone have any suggestions ? > > The only situation in which the crystal drive level might be an issue is > in some ancient single stage tube transmitters (prior to 1960's). For > any embedded application, the crystal power limit should not be an > issue. > > For frequencies above 20 MHz you might need a circuit suitable for an > overtone crystal. > > PaulAFAIK the little strip-cut crystals aren't compatible with older IC drive circuits -- at least there were warnings out at the time they became available. I've never had occasion to build a circuit where I had to check, though. -- Tim Wescott Control systems and communications consulting http://www.wescottdesign.com Need to learn how to apply control theory in your embedded system? "Applied Control Theory for Embedded Systems" by Tim Wescott Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
