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SN74HC4020: Propagation Delay

fujiitk
Prodigy 40 points
Part Number: SN74HC4020

Hello,

I have a question about the propagation delay of "SN74HC4020" .

The data sheet only lists the propagation delay from CLK to QA.
How do I calculate the propagation delay from QA to other outputs?

Best regards.

  • 0
    TI__Intellectual 2111 points

    Hello,

    We don't have exact numbers for propagation delay from other outputs besides CLK to QA in the datasheet. You can estimate that the propagation delay across the internal flip flops are the same as the propagation delay from CLK to QA, so the propagation delay from QA to QB would be tpd(CLK_QA) and the propagation delay from QA to QD would be 3*tpd(CLK_QA) . I hope this helps!

    Best regards,

    Ian

  • 0
    Prodigy 40 points

    Hi Ian,

    Thank you for answering.

    In other manufacturer's datasheet, the tpd of CLK_QA is about half of Qn_Qn+1.

    Won't the value become too large when calculated with n*tpd(CLK_QA)?

    Best regards.

  • 0 in reply to fujiitk
    TI__Intellectual 2111 points

    Hi,

    Our 74hc4020 devices perform similar to our competitors, so it is reasonable to assume that the tpd between outputs will follow a similar trend. However, we only guarantee what's in the datasheet, so I gave you a worst-possible-scenario estimate.