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  • TI Thinks Resolved

CD4027B: The otput Q won't change

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Replies: 11

Views: 401

Part Number: CD4027B

Dear *,

I attached my schematic with CD4027B. I have connected toggle button on P2 and when press the button the 14V comes to K1, J1 and through R10 10Ohm C8 100n to CLK1 but the Q1 is always 12V and Q1_n always 0V

please can you help?

BR.

TOGGLE-BUTTON.pdf 

  • In reply to ZeroD:

    Hi ZeroD,

    I believe what Dylan is looking for is oscillation on the CD4050B. This is a standard CMOS device and it will oscillate at the output when presented with a very slow input transition (which is what is happening in your circuit).

    You probably haven't seen the oscillations since they are probably happening at ~10ns time scale, and all the scope shots here are at ~2us/pt (about 2000x to large to see the problem).

    Here's an FAQ that talks about what's happening:

     

    If you swap the CD4050B for a CD40106B (hex Schmitt-trigger inverter) it will remove this problem, however you will need to invert your button logic values (or use 2 stages of the inverter).  Here's more info on Schmitt-triggers and why you need them: 


    Looking for a low voltage translator? Check out the AXC family that supports 0.7V to 3.3V translation!

    The Logic Minute training page has videos on many interesting topics that all are kept shorter than 5 minutes.

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