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CD74HC4046A: Minimum Frequency

Part Number: CD74HC4046A

Hi Team,

Our customer would like to know the minimum frequency range of CD74HC4046AM and if this device can support a frequency range of High Signal: 890Hz, Low Signal: 730 Hz.

I looked at the datasheet and found no minimum value on the specification table. 

In addition to this, the customer is also requesting a similar device with the spec of 100 – 420 Hz

Thank you for the help.


Marvin A.

  • Hi Marvin,

    The datasheet shows operation down to about 4 Hz with a 0.1uF capacitor and 11Mohm resistor:

    I highlighted 100 Hz operation, using R1 = 11Mohm or 2.2Mohm.

    Larger capacitors can be used also to get slower ranges from smaller resistor values. For example, a 1uF capacitor could be used with a 22kohm resistor to get about 100 Hz also.

    Because the timing method uses constant current sources, the capacitor value isn't limited - ie it doesn't cause a loading issue. Just don't use a polarized capacitor, as it has to charge in both directions.