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2006-08-12 by magzky02
hello to everyone... i am looking for a precise SMT crystal that has temperature compensation feature ... anyone have seen such product in the internet? i had searched dozens of crystal manufacturers but i didnt see one. i dont know if such product really exist. most crystals available have -0.03 to -0.04 PPM/C^2(degree celcius squared) at -40C to 85C temperature range. mago
2006-08-12 by Ned Konz
magzky02 wrote: > hello to everyone... > > i am looking for a precise SMT crystal that has temperature > compensation feature ... anyone have seen such product in the internet? > i had searched dozens of crystal manufacturers but i didnt see one. > i dont know if such product really exist. > most crystals available have -0.03 to -0.04 PPM/C^2(degree celcius > squared) at -40C to 85C temperature range. Seems like you could put a resistor next to the crystal and a thermistor and just hold a temperature (use a power transistor and PWM to vary the heat from the resistor). Thanks, -- Ned Konz ned@bike-nomad.com http://bike-nomad.com
2006-08-12 by David VanHorn
> i am looking for a precise SMT crystal that has temperature > compensation feature ... anyone have seen such product in the internet? > i had searched dozens of crystal manufacturers but i didnt see one. > i dont know if such product really exist. > most crystals available have -0.03 to -0.04 PPM/C^2(degree celcius > squared) at -40C to 85C temperature range. Precision oscillator design is somewhat of an art. You'll need more than just a stable crystal. Getting the crystal isn't that hard, just email Statek, or one of the others, and tell them your requirements. They can do customs. The rest of the circuit will need to be designed though.. The caps and resistors selected to match the crystal, and the rest. For example, I have a couple of repeaters that use crystals to determine transmit and receive frequency. They do NOT use any ovens, the whole thing draws less than 30mA on standby :) But the oscillator circuits have seven thermistors, and are quite complicated. 5ppm -40C to +60C is guaranteed. It's the sort of thing that you typically helicopter to the peak of a mountain and leave for a few years. [Non-text portions of this message have been removed]
2006-08-12 by David VanHorn
> > > Seems like you could put a resistor next to the crystal and a thermistor > and just hold a temperature (use a power transistor and PWM to vary the > heat from the resistor). They make xtal ovens like this, but the power consumption is a problem in many applications. In my repeater application, the oven would be about 200mA with the rest of the repeater drawing 30mA Makes a BIG difference if you're solar powering, and none at all if you can plug into the wall. Battery backup time is affected, but for us if there's something going on that knocks out the power, then the system will likely be busy, and the transmitters draw WAY more power (100W and 80W) than the ovens. Just depends on the application. Digital watches normally use a precision heater, and far larger than you'd think. [Non-text portions of this message have been removed]
2006-08-12 by John Samperi
At 06:49 PM 12/08/2006, you wrote: >i am looking for a precise SMT crystal that has temperature >compensation feature ... Dallas (Maxim) make them for clock circuits at 32KHz (DS32KHz) Regards John Samperi ******************************************************** Ampertronics Pty. Ltd. 11 Brokenwood Place Baulkham Hills, NSW 2153 AUSTRALIA Tel. (02) 9674-6495 Fax (02) 9674-8745 Email: john@ampertronics.com.au Website http://www.ampertronics.com.au *Electronic Design * Custom Products * Contract Assembly ********************************************************
2006-08-13 by Jim Wagner
Just a "temperature compensated crystal" won't do it. At that level, the oscillator, itself has a major effect. Instead, a TCXO (Temperature Compensated Xtal Oscillator) is needed. This is an entire oscillator plus crytal in a "box" and compensated, often digitally. Jim On Sat, 12 Aug 2006 16:40:37 -0400 "David VanHorn" <microbrix@gmail.com> wrote: > > i am looking for a precise SMT crystal that has > temperature > > compensation feature ... anyone have seen such product > in the internet? > > i had searched dozens of crystal manufacturers but i > didnt see one. > > i dont know if such product really exist. > > most crystals available have -0.03 to -0.04 > PPM/C^2(degree celcius > > squared) at -40C to 85C temperature range. > > > Precision oscillator design is somewhat of an art. > You'll need more than just a stable crystal. > Getting the crystal isn't that hard, just email Statek, > or one of the > others, and tell them your requirements. They can do > customs. > > The rest of the circuit will need to be designed though.. > The caps and > resistors selected to match the crystal, and the rest. > > For example, I have a couple of repeaters that use > crystals to determine > transmit and receive frequency. They do NOT use any > ovens, the whole thing > draws less than 30mA on standby :) But the oscillator > circuits have > seven thermistors, and are quite complicated. > 5ppm -40C to +60C is guaranteed. It's the sort of thing > that you typically > helicopter to the peak of a mountain and leave for a few > years. > > > [Non-text portions of this message have been removed] > --------------------------------------------------------------- The Think Different Store http://www.thinkdifferentstore.com/ For All Your Mac Gear ---------------------------------------------------------------
2006-08-13 by mago Umandam
30mA on standby consumption is too high for my application since it is battery operated and left in field. so i have to change my priority from stability to low power consumption..has anyone come accross an ultra low power RTC ( less than 10 uA on standby)? seems dallas RTC's dont go as low as that.
Jim Wagner <jim_d_wagner@applelinks.net> wrote:
Just a "temperature compensated crystal" won't do it. At
that
level, the oscillator, itself has a major effect. Instead,
a
TCXO (Temperature Compensated Xtal Oscillator) is needed.
This is an entire oscillator plus crytal in a "box" and
compensated,
often digitally.
Jim
On Sat, 12 Aug 2006 16:40:37 -0400
"David VanHorn" <microbrix@gmail.com> wrote:
> > i am looking for a precise SMT crystal that has
> temperature
> > compensation feature ... anyone have seen such product
> in the internet?
> > i had searched dozens of crystal manufacturers but i
> didnt see one.
> > i dont know if such product really exist.
> > most crystals available have -0.03 to -0.04
> PPM/C^2(degree celcius
> > squared) at -40C to 85C temperature range.
>
>
> Precision oscillator design is somewhat of an art.
> You'll need more than just a stable crystal.
> Getting the crystal isn't that hard, just email Statek,
> or one of the
> others, and tell them your requirements. They can do
> customs.
>
> The rest of the circuit will need to be designed though..
> The caps and
> resistors selected to match the crystal, and the rest.
>
> For example, I have a couple of repeaters that use
> crystals to determine
> transmit and receive frequency. They do NOT use any
> ovens, the whole thing
> draws less than 30mA on standby :) But the oscillator
> circuits have
> seven thermistors, and are quite complicated.
> 5ppm -40C to +60C is guaranteed. It's the sort of thing
> that you typically
> helicopter to the peak of a mountain and leave for a few
> years.
>
>
> [Non-text portions of this message have been removed]
>
----------------------------------------------------------
The Think Different Store
http://www.thinkdifferentstore.com/
For All Your Mac Gear
----------------------------------------------------------
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[Non-text portions of this message have been removed]2006-08-14 by David VanHorn
On 8/13/06, mago Umandam <magzky02@yahoo.com> wrote: > > 30mA on standby consumption is too high for my application since it is > battery operated and left in field. so i have to change my priority from > stability to low power consumption..has anyone come accross an ultra low > power RTC ( less than 10 uA on standby)? seems dallas RTC's dont go as low > as that. You'll be looking for something that uses the Vittoz mode oscillators, and crystal/cap selection will be very critical. [Non-text portions of this message have been removed]
2006-08-14 by Bob Paddock
On Sunday 13 August 2006 02:49, mago Umandam wrote:
> 30mA on standby consumption is too high for my application since it is battery operated and left in field.
> so i have to change my priority from stability to low power consumption..has anyone come accross an ultra low power RTC
> ( less than 10 uA on standby)? seems dallas RTC's dont go as low as that.
Micro-Crystal has temperature compensated RTC's, that give 32,767 Hz out.
400 nano-amps on standby, don't don't think you'll find lower.
http://www.microcrystal.ch/Products.aspx?CatalogID=1&HasFlash=true
--
http://www.softwaresafety.net/ http://www.designer-iii.com/
http://www.unusualresearch.com/2006-08-14 by mago Umandam
thank you bob.. they are pretty good for my application...
Bob Paddock <bob.paddock@gmail.com> wrote: On Sunday 13 August 2006 02:49, mago Umandam wrote:
> 30mA on standby consumption is too high for my application since it is battery operated and left in field.
> so i have to change my priority from stability to low power consumption..has anyone come accross an ultra low power RTC
> ( less than 10 uA on standby)? seems dallas RTC's dont go as low as that.
Micro-Crystal has temperature compensated RTC's, that give 32,767 Hz out.
400 nano-amps on standby, don't don't think you'll find lower.
http://www.microcrystal.ch/Products.aspx?CatalogID=1&HasFlash=true
--
http://www.softwaresafety.net/ http://www.designer-iii.com/
http://www.unusualresearch.com/
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