Crystal Oscillator problem

Discussion in 'Electronic Design' started by Mig, Sep 7, 2007.

  1. Mig

    Mig Guest

    I encountered with very strange problem with a ceramic crystal
    oscillator.
    It took a long time to recreate the problem.
    When a power supply voltage is turned on first time there is no output
    frequency. When the power supply is turned off and on again the
    frequency appears.
    You can see it on the video here.
    http://www.youtube.com/watch?v=9mWOWL4LGsU
    Any suggestions?
    The vendor doesn't know why it happens. :(
    Mig, Sep 7, 2007
    #1
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  2. Mig

    Don Bowey Guest

    On 9/7/07 7:51 AM, in article
    , "Mig"
    <> wrote:

    > I encountered with very strange problem with a ceramic crystal
    > oscillator.
    > It took a long time to recreate the problem.
    > When a power supply voltage is turned on first time there is no output
    > frequency. When the power supply is turned off and on again the
    > frequency appears.
    > You can see it on the video here.
    > http://www.youtube.com/watch?v=9mWOWL4LGsU
    > Any suggestions?
    > The vendor doesn't know why it happens. :(
    >


    Post the schematic somewhere. Too little gain or feedback.
    Don Bowey, Sep 7, 2007
    #2
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  3. On Fri, 07 Sep 2007 14:51:09 -0000, Mig <>
    wrote:

    >I encountered with very strange problem with a ceramic crystal
    >oscillator.


    Ceramic or crystal? They're different animals.

    >It took a long time to recreate the problem.
    >When a power supply voltage is turned on first time there is no output
    >frequency. When the power supply is turned off and on again the
    >frequency appears.
    >You can see it on the video here.
    >http://www.youtube.com/watch?v=9mWOWL4LGsU
    >Any suggestions?
    >The vendor doesn't know why it happens. :(


    It could be an analog problem with the start-up (eg. load capacitors
    wrong or not enough gain, or biasing not present) or it could be
    something else entirely like your circuit (if it's some complex chip)
    going into sleep mode or whatever. Best show us the complete circuit--
    and don't expect oscillators built on plug breadboards (if that's
    what you have) to work reliably.


    Best regards,
    Spehro Pefhany
    --
    "it's the network..." "The Journey is the reward"
    Info for manufacturers: http://www.trexon.com
    Embedded software/hardware/analog Info for designers: http://www.speff.com
    Spehro Pefhany, Sep 7, 2007
    #3
  4. Mig

    Mig Guest

    On Sep 7, 11:04 am, Spehro Pefhany <>
    wrote:
    > On Fri, 07 Sep 2007 14:51:09 -0000, Mig <>
    > wrote:
    >
    > >I encountered with very strange problem with a ceramic crystal
    > >oscillator.

    >
    > Ceramic or crystal? They're different animals.
    >
    > >It took a long time to recreate the problem.
    > >When a power supply voltage is turned on first time there is no output
    > >frequency. When the power supply is turned off and on again the
    > >frequency appears.
    > >You can see it on the video here.
    > >http://www.youtube.com/watch?v=9mWOWL4LGsU
    > >Any suggestions?
    > >The vendor doesn't know why it happens. :(

    >
    > It could be an analog problem with the start-up (eg. load capacitors
    > wrong or not enough gain, or biasing not present) or it could be
    > something else entirely like your circuit (if it's some complex chip)
    > going into sleep mode or whatever. Best show us the complete circuit--
    > and don't expect oscillators built on plug breadboards (if that's
    > what you have) to work reliably.
    >
    > Best regards,
    > Spehro Pefhany
    > --
    > "it's the network..." "The Journey is the reward"
    > Info for manufacturers:http://www.trexon.com
    > Embedded software/hardware/analog Info for designers: http://www.speff.com


    Sorry my mistake. This is no a crystal. It is a ceramic.
    There is no schematic.
    The part comes with 4 pins, Power, GND, Enable and Frequency output.
    I'm just testing the bad part that malfunctioned on the board.
    I connected just a power and hooked the oscilloscope to the output.
    That the first time ever I have encountered with the problem with the
    ceramic oscillator!
    Mig, Sep 7, 2007
    #4
  5. Mig

    Tim Shoppa Guest

    On Sep 7, 10:51 am, Mig <> wrote:
    > I encountered with very strange problem with a ceramic crystal
    > oscillator.
    > It took a long time to recreate the problem.
    > When a power supply voltage is turned on first time there is no output
    > frequency. When the power supply is turned off and on again the
    > frequency appears.
    > You can see it on the video here.http://www.youtube.com/watch?v=9mWOWL4LGsU
    > Any suggestions?
    > The vendor doesn't know why it happens. :(


    Desiging an oscillator that will start up reliably 100 percent of the
    time is far more difficult than designing an oscillator that works
    most of the time.

    This is a pre-canned oscillator, right? Or wrong?

    Most of the pre-canned oscillators are pretty good. But look carefully
    at the output load capacitance specs. If this is a canned oscillator
    designed to put out a digital train, and it's putting out a sine wave
    (what I see on the scope!), you must have a lot of capacitive load on
    the output.

    If it's not a canned oscillator, it looks like your oscillator is not
    going into deep saturation after startup (that looks like a sine wave
    on the scope), so more gain would help with startup. (Not necessarily
    reliable startup! You will find with too much gain that you start mode-
    hopping or stick to some mode you didn't want to excite.)

    Tim.
    Tim Shoppa, Sep 7, 2007
    #5
  6. Mig

    Jamie Guest

    Mig wrote:

    > On Sep 7, 11:04 am, Spehro Pefhany <>
    > wrote:
    >
    >>On Fri, 07 Sep 2007 14:51:09 -0000, Mig <>
    >>wrote:
    >>
    >>
    >>>I encountered with very strange problem with a ceramic crystal
    >>>oscillator.

    >>
    >>Ceramic or crystal? They're different animals.
    >>
    >>
    >>>It took a long time to recreate the problem.
    >>>When a power supply voltage is turned on first time there is no output
    >>>frequency. When the power supply is turned off and on again the
    >>>frequency appears.
    >>>You can see it on the video here.
    >>>http://www.youtube.com/watch?v=9mWOWL4LGsU
    >>>Any suggestions?
    >>>The vendor doesn't know why it happens. :(

    >>
    >>It could be an analog problem with the start-up (eg. load capacitors
    >>wrong or not enough gain, or biasing not present) or it could be
    >>something else entirely like your circuit (if it's some complex chip)
    >>going into sleep mode or whatever. Best show us the complete circuit--
    >>and don't expect oscillators built on plug breadboards (if that's
    >>what you have) to work reliably.
    >>
    >>Best regards,
    >>Spehro Pefhany
    >>--
    >>"it's the network..." "The Journey is the reward"
    >> Info for manufacturers:http://www.trexon.com
    >>Embedded software/hardware/analog Info for designers: http://www.speff.com

    >
    >
    > Sorry my mistake. This is no a crystal. It is a ceramic.
    > There is no schematic.
    > The part comes with 4 pins, Power, GND, Enable and Frequency output.
    > I'm just testing the bad part that malfunctioned on the board.
    > I connected just a power and hooked the oscilloscope to the output.
    > That the first time ever I have encountered with the problem with the
    > ceramic oscillator!
    >

    So , your repairing?


    --
    "I'm never wrong, once i thought i was, but was mistaken"
    Real Programmers Do things like this.
    http://webpages.charter.net/jamie_5
    Jamie, Sep 7, 2007
    #6
  7. Mig

    legg Guest

    On Fri, 07 Sep 2007 14:51:09 -0000, Mig <>
    wrote:

    >I encountered with very strange problem with a ceramic crystal
    >oscillator.
    >It took a long time to recreate the problem.
    >When a power supply voltage is turned on first time there is no output
    >frequency. When the power supply is turned off and on again the
    >frequency appears.
    >You can see it on the video here.
    >http://www.youtube.com/watch?v=9mWOWL4LGsU
    >Any suggestions?
    >The vendor doesn't know why it happens. :(


    Looked like it actually was encouraged to start as the first
    application of power was in the process of being removed.

    Try delaying the enable signal. You don't indicate how it is being
    connected - assume currently a short to appropriate logic.

    Check it's spec for minimum/maximum dv/dt on the supply pin.
    Check it's application supply voltage range.

    RL
    legg, Sep 7, 2007
    #7
  8. Mig

    Eeyore Guest

    Mig wrote:

    > I encountered with very strange problem with a ceramic crystal
    > oscillator.
    > It took a long time to recreate the problem.
    > When a power supply voltage is turned on first time there is no output
    > frequency. When the power supply is turned off and on again the
    > frequency appears.
    > You can see it on the video here.
    > http://www.youtube.com/watch?v=9mWOWL4LGsU
    > Any suggestions?
    > The vendor doesn't know why it happens. :(


    The vendor is useless in that case. Find a new vendor.

    Is that an oscillator *module* btw or one you built with the vendor's crystal ?

    Graham
    Eeyore, Sep 8, 2007
    #8
  9. Mig

    Mig Guest

    On Sep 7, 10:47 pm, Eeyore <>
    wrote:
    > Mig wrote:
    > > I encountered with very strange problem with a ceramic crystal
    > > oscillator.
    > > It took a long time to recreate the problem.
    > > When a power supply voltage is turned on first time there is no output
    > > frequency. When the power supply is turned off and on again the
    > > frequency appears.
    > > You can see it on the video here.
    > >http://www.youtube.com/watch?v=9mWOWL4LGsU
    > > Any suggestions?
    > > The vendor doesn't know why it happens. :(

    >
    > The vendor is useless in that case. Find a new vendor.
    >
    > Is that an oscillator *module* btw or one you built with the vendor's crystal ?
    >
    > Graham


    The part is a module. So there is no option for tweaking gain or
    something else.
    So far there were no problems with this vendor. But there is always
    first time. :(
    I have not heard from him since I sent him a link with the video.
    I have already ordered samples form another company.
    Mig, Sep 8, 2007
    #9
  10. Mig

    Eeyore Guest

    Mig wrote:

    > Eeyore <> wrote:
    > > Mig wrote:
    > > > I encountered with very strange problem with a ceramic crystal
    > > > oscillator.
    > > > It took a long time to recreate the problem.
    > > > When a power supply voltage is turned on first time there is no output
    > > > frequency. When the power supply is turned off and on again the
    > > > frequency appears.
    > > > You can see it on the video here.
    > > >http://www.youtube.com/watch?v=9mWOWL4LGsU
    > > > Any suggestions?
    > > > The vendor doesn't know why it happens. :(

    > >
    > > The vendor is useless in that case. Find a new vendor.
    > >
    > > Is that an oscillator *module* btw or one you built with the vendor's crystal ?

    >
    >
    > The part is a module. So there is no option for tweaking gain or
    > something else.


    Understood.


    > So far there were no problems with this vendor. But there is always
    > first time. :(
    > I have not heard from him since I sent him a link with the video.
    > I have already ordered samples form another company.


    That sounds like the best idea.

    Graham
    Eeyore, Sep 8, 2007
    #10
  11. Mig

    Guest

    On Sep 7, 7:51 am, Mig <> wrote:
    > I encountered with very strange problem with a ceramic crystal
    > oscillator.
    > It took a long time to recreate the problem.
    > When a power supply voltage is turned on first time there is no output
    > frequency. When the power supply is turned off and on again the
    > frequency appears.
    > You can see it on the video here.http://www.youtube.com/watch?v=9mWOWL4LGsU
    > Any suggestions?
    > The vendor doesn't know why it happens. :(


    That is the geekiest video I ever saw on youtube. ;-)

    I see that you are powering up a bench supply to start the module.
    Often these bench supplies have a soft start feature. Your module may
    not like the supply to be ramped slowly. Try leaving the supply on and
    just connecting the DC to the module, that is, hit it hard.
    , Sep 8, 2007
    #11
  12. Mig

    Phil Hobbs Guest

    Mig wrote:
    > I encountered with very strange problem with a ceramic crystal
    > oscillator.
    > It took a long time to recreate the problem.
    > When a power supply voltage is turned on first time there is no output
    > frequency. When the power supply is turned off and on again the
    > frequency appears.
    > You can see it on the video here.
    > http://www.youtube.com/watch?v=9mWOWL4LGsU
    > Any suggestions?
    > The vendor doesn't know why it happens. :(
    >


    Startup problems are as common as dirt.

    Most oscillators work in a large-signal regime where the active devices
    are nonlinear. Thus the average gain, impedance level, and feedback are
    all different when the oscillator is running, compared with the same
    circuit in a quiescent state.

    The feedback loop may well be stable at small-signal conditions and only
    oscillatory at large signal conditions. If the power supply transient
    is quicker than the bias time constant of the oscillator, it'll find
    itself in a large-signal condition at power-up, which will get the
    oscillator going and mask the startup problem. It's really important to
    test oscillators under a wide variety of turn-on conditions, including
    very slow ramps.

    It's also quite possible for oscillators to have too much feedback, in
    which case you get all sorts of distortion and self-modulation rather
    than a nice CW sine wave. ALC oscillators adjust their loop gain based
    on oscillation amplitude, and thus tend to avoid both kinds of problem
    (as well as being much quieter).

    I gather that your power supply is producing different turn-on
    transients, depending on how long it has been switched off. From the
    symptoms, it appears that when it's been off long enough for the filter
    caps to have discharged, the turn-on is slower than when you turn it off
    and then on again, and the difference is enough to expose the startup
    problem.

    Cheers,

    Phil Hobbs
    Phil Hobbs, Sep 10, 2007
    #12
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