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LM567CN Circuit not Triggering

Michael Rizzo
Prodigy 40 points

Hello,

I am looking to use the LM567 tone decoder circuit. I believe I have followed all of the steps on the datasheet correctly. I set the center frequency using 1.1/(R1*C1), and then I set the bandwidth using table 2 and the center frequency in kHz. However, after I follow this procedure the output of the circuit does not change.

Note that I use C2=1uF, C3=2.2uF (both ceramic), Cin=1uF, Ro=27kOhm, C1=0.1uF and R1=314ohm and Vcc=5V. Also I am using a somewhat idealized input waveform at the moment, in an attempt to just get the output to behave correctly. It is a 35kHz sinusoidal waveform with a peak voltage of 2.5V. I try both pulsed wave and continuous wave, but neither seems to work. Any help would be much appreciated.

Mike

  • 0
    TI__Mastermind 20085 points
    Hi Michael

    Welcome to E2E, thanks for your interest in our products.
    I can't watch the file that you downloaded, Could you show me how you made the calculations and provide me a schematic?

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | LPAA
  • 0 in reply to José Luis
    Prodigy 40 points
    I used the formula F0= 1.1/(R1*C1), and then I used table 2 on the datasheet to determine the bandwidth. Note that I choose the widest bandwidth possible for initial tests. Please note that I am applying a 35kHz signal on the input and want the center frequency to be around 35kHz.

    For the schematic please go to page 19 of the datasheet. I listed all of the relevant parts in my original post.

    Also, one thing I haven't tried yet, if I probe pin 5 or 6, is it possible to measure the oscillation frequency, as set by R1/C1 of the vco?
  • 0 in reply to Michael Rizzo
    TI__Mastermind 20085 points

    Michael,

    I have reviewed and that seems to be correct. I have some questions for you, Which are the tolerances the used components? and what are you getting in the output device?

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | LPAA

  • 0 in reply to José Luis
    Prodigy 40 points

    The output of the device remains high, and never triggers. The tolerances are not too high. The capacitors are probably +/-10% and the resistors are probably 1% or 5%. When I measure their values, however, they still seem to be close enough to the center frequency of the part. I have a question, did you measure this in the lab or did you just perform a hand calculation from the datasheet?

  • 0 in reply to José Luis
    Prodigy 40 points

    I managed to resolve the issue today. Thanks.

  • 0 in reply to Michael Rizzo
    TI__Mastermind 20085 points
    Michael,

    How did you resolve this issue?
    Please share this information, this could be useful for other customer with the same problem.

    Best Regards
    Jose Luis Figueroa
    Audio Applications Engineer | LPAA