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  1. #1
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    [moved] 74HC4060 Oscillator/Counter Frequeny Problem

    Hello,
    I have an oscillator/counter (74HC4060) which is part of a 100%-properly-working board. The oscillator with the external resistors and capacitors, generates a 73.5 kHz pulse (pin # 9, which is CTC). I'm trying to copy this oscillator in another board and I'm using the exact R & C values on the reference board. What I get is a 78 kHz pulse. So, this is the first problem.

    Then, I checked the datasheet to understand about the R & C values and how I should change them to get the 73.5 kHz. The datasheet says the oscillation frequency is given by the formula: fosc = 1/(2.5*R*C), but when I put the R & C values in the formula I get 120 kHz. So, this is my second problem.

    1- Why do I get a different frequency from the reference board?
    2- Why does the oscillation frequency of the reference board differs from what the datasheet says?

    I'm attaching the circuit.

    Click image for larger version. 

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    Thank you.

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  2. #2
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    Re: 74HC4060 Oscillator/Counter Frequeny Problem

    Hi,

    Show a photo of your circuit, where we can see all your connections.

    There are many manufacturers that produce HC4060. Please tell us the exact part name and manufacturer.
    It would be very kind of you to upload (a link to) the datasheet of the your manufacturer.

    73.5kHz and 78kHz are off by about 6%. Many capacitors have a tolerance of +/-20%, or +/-10% .... thus 78kHz may be within tolerance.
    --> give use exact type and manufacturer of all your Rs and Cs. ... and datasheets.
    Also the HC4060 as well as the resistors and the power supply have tolerance.
    The wiring causes additional impedances that will shift the frequency, thus I asked for a photo.
    Even the connection to your frequency meter will have influence to the frequency.
    And: don't let (unused) inputs floating.
    --> It's not surprising to get 78kHz.

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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