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CD4017 - Does it still have a Schmitt trigger clock input?

Clive Tobin
Prodigy 20 points

I recently bought 100 pieces of TI CD4017BE from (I am ashamed to say) not an authorized distributor. This part is supposed to have Schmitt trigger clock input on pin 14 according to your data sheet. However, feeding in a signal with a slightly slow rise time, but no unusual noise, I am getting multiple triggerings. I wonder have you changed this part so you are no longer using the RCA / Harris design with Schmitt input, but have changed to the National design which lacked the Schmitt trigger input and requires a fast rise time? Or did someone slip me some fake parts? They have the TI "Texas" logo and are marked 2TCIFCM and CD4017BE on top and A7 underneath.

  • 0
    TI__Guru* 96862 points

    Clive,

    The design hasn't changed on the CD4017BE -- it still has a Schmitt-trigger input on the clock and should accept slow/noisy inputs without issues.

    If you want to verify the markings on the device, there's a document here that talks about how we mark standard linear/logic parts.

    Assuming that you determine these are genuine parts, I can try to help troubleshoot what's going on.  Can you get me scope shots of the clock, Vcc, and Ground at the pins of the device?  Also, a schematic would be helpful.

  • 0
    Prodigy 20 points

    I believe these parts are counterfeit and they were sourced from China. Replacing them with a genuine TI part from a USA distributor the circuit works perfectly.