propagation delay of sn74hc125

[khaled ragab]

hello i am confused about the propagation delay and the rise and fall time the datasheet here https://www.ram-e-shop.com/ds/74xx/74125.pdf express tpd=30ns for example, but the rise and fall time delay is 500ns how can i calculate the whole delay

 

[zuisti]

hello i am confused about the propagation delay and the rise and fall time the datasheet here https://www.ram-e-shop.com/ds/74xx/74125.pdf express tpd=30ns for example, but the rise and fall time delay is 500ns how can i calculate the whole delay

Hi;
The above 500 ns is the maximum allowed rise and fall time of the input waweform (input transition rise/fall time), NOT a delay !!!
The max. whole delay is (at 25 degr, 50 pF and 4.5 V) is appr 30 ns (Tplh or Tphl = Tpd, from/to the 50% of the input transition, see the figure)