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CD4060B: Variation of Frequency (Unit-to-Unit) - datasheet interpretation

Oliver Filsch
Intellectual 260 points
Part Number: CD4060B

Hello,

on page 4 of the datasheet there is information about the variation of frequency (unit-to-unit).

For example, with Cx=200pF, Rx=50k, the resulting oscillation frequency according to formula on page 3 would be 1/(2.2*Rx*Cx) = 45.455kHz.

The table states for Vdd=5V a variation of 23 +/-10% kHz.

I do not assume that there is 23kHz variation at a nominal frequency of 45kHz.

How are the values in the table to be understood?

  • 0
    TI__Guru* 96681 points

    Hi Oliver,

    I would expect better performance unit-to-unit for frequency variation also. This type of oscillator is primarily affected by variations in output drive strength (R) and input capacitance (C), neither of which should change enough to warrant a 50% shift in frequency (with 50k and 200pF timing components).

    Unfortunately, a lot of information has been lost to time with these older Harris parts.  TI acquired these about 20 years ago with limited data. I don't have char data to refer to, and I don't know why this spec was chosen this way.

    That being said, I can only guarantee what the datasheet lists -- so if the device does have 20 kHz of variation, that would be an expected behavior based on this spec. If you need more accuracy, I would recommend to use a crystal oscillator instead of an RC oscillator.