4 terminal crystal oscillator and schematic symbol

Discussion in 'General Electronics Chat' started by hunterage2000, Jan 17, 2013.

  1. hunterage2000

    Thread Starter Active Member

    May 2, 2010
    400
    0
    I have a 4 terminal crystal oscillator and I want to know how I connect it in a circuit. The four terminals are vdd, gnd, out and OE or ST(NOT) but on schematics the symbol is just 2 terminals. Can anyone tell me what these 2 terminals are?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,791
    I doubt it, but it would help if you showed us the schematic you are looking at.
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,016
    3,235
    What schematics?

    The two terminals are likely for a bare crystal, not a crystal oscillator which contains a crystal and circuitry to generate the oscillation.
     
  4. hunterage2000

    Thread Starter Active Member

    May 2, 2010
    400
    0
    Yeah here it is.
     
  5. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    The "schematic" is a functional equivalent, as such, you don't care if the supply is 3V or 5V(though the device may). As far as it's function, ground and out are the important signals, though OE should be also(don't know why it isn't :confused:).
     
  6. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,058
    3,820
    OE is probably "oscillator enable". You need to pull it up to Vcc to make it operate. "ST" is some phrase that is not coming to me that likely means the opposite of "oscillator enable" that would mean you have to tie it to ground to make it stop working.
     
  7. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,058
    3,820
    Try connecting just the power and OE pins to power and checking that it oscillates. You may not need the external circuitry as most 4-pin oscillators do not.
     
  8. Papabravo

    Expert

    Feb 24, 2006
    10,144
    1,791
    Yeah... pay no attention to what the other guys said. Pay attention to what crutschow said. The schematic shows a crystal. The crystal plus the inverter and the capacitor and the resistor make a "crystal oscillator". With the 4-terminal device you don't need the other components. You hook up Vcc to a voltage source. Read the datasheet for "Absolute Maximum Ratings" and typical operation values. Vcc should have a bypass capacitor to GND. GND should go to Ground. OE can be controlled by a logic signal if you want to turn the oscillator on and off. You can also tie it to VCC (since OE looks like it is active high and low would be STOP) to have the oscillator on all the time, and the output is your holy grail.
     
    Last edited: Jan 17, 2013
  9. t06afre

    AAC Fanatic!

    May 11, 2009
    5,939
    1,222
    I would say then pin 1 is high. You will have an output from the oscillator. OE probably is short for Output Enable. Then low in ST mode (probably STandby mode). It is common that oscillator output goes to the high impedance state. But this may vary from device to device
     
  10. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
  11. hunterage2000

    Thread Starter Active Member

    May 2, 2010
    400
    0
    Thanks for the links ScottWang, The datasheet for mine doesnt actually say how the oscillator is used. It just shows what the pins are and what they do. I tried wiring it up with OE/ST attached to VCC and GND but the oscilloscope just shows either a 10mV voltage for GND and A random 2.5V output.

    Has anyone used one of these oscillators before? and what components were connected to it?

    Also I read that crystal oscillators produce the most accurate and stable square-waves, Is this right? and if not can someone recommend one. I have attached a section from one of my books that states the four pins and shows a diagram of it in a circuit.

    I tried putting capacitors between GND pin and GND rail and between OE/ST and GND rail but didnt work.
     
  12. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    A Bypass Capacitor between Vdd and Gnd is the only other component you could need.

    The precision of clock chips means that they always include the capacitor shown on the functional schematic inside the chip package.

    You only need two supply connections - count OE and Vdd as one since they are normally tied together to your source, and gnd is on the gnd pin.

    You have one output pin. If that output is random then the most likely explanation is that the CMOS is leaky - probably damaged by an Electro Static Discharge.

    On some schematics, Vdd and Ground might not be shown, so you might only see the OE and Output.
     
  13. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    Do you have more details about your oscillator? (No., Brand,datasheet,etc)

    Assuming that your oscillator is a fixed frequency type, and only use OE /ST to control it to Out or Not output.

    OE /ST : Input High or Open to enable the output, input Low to disable the output.

    As the way you tried, if it didn't work, maybe it is damaged or it is another type.

    The linked page shows on below is a programable oscillator, OE/ST pin also is a prog pin, please look the last linked page on page 7 for internal structures.

    OE /ST -- Standby/ Output Enable
    http://www.sitime.com/products/datasheets/sit8102/SiT8102-datasheet.pdf

    Silicon MEMS Oscillators for High Speed Digital Systems
    http://www.hotchips.org/wp-content/...1.25.640.Partridge-SiTime-MEMS-Oscillator.pdf
     
Loading...