Warning: Your Pin-Compatible ICs Are Lying To You! (And Why It Matters)

Today, I want to talk about two ICs with the same footprint and the same function, yet they may not work interchangeably.

The ICs in this discussion are the hex buffer, CD4050B and 74HC04. To someone starting in electronics, these may look the same in terms of the function, physical footprint and pinout. One might assume these can be interchanged. Well, not quite.

Since they belong to different families, there is an electrical difference within the IC.

The older CD4000 series can have around 5 to 10 times longer rise times. And from the previous post about TEL, the length of the trace where the signal integrity issues start is different for each. So if you drop in the new 74HC04 buffer in a design with long traces, the system will have issues.

When you find a Pin-compatible replacement for your IC for one the components, check out the rise times.