I need to figure this out for a project and can't seem to find the answer. Does anyone know how I can figure this out? I think there is an equation to find this and can't seem to find the specification sheet for MC9S12DG128. What do I need to figure out about the MC9S12 to find the answer?

# How many 74LS low-power Schottky inputs can an output of MC9S12DG128 drive

low-powerschottky

## Best Answer

The MC9S12DG128 can sink or source an absolute maximum of 25mA from any GPIO pin (as stated in the datasheet).

The 74LS00 has \$I_{IH}\$ (in the example I found) of 20µA. It has an \$I_{IL}\$ of 0.4mA though, which is higher.

25mA / 0.4mA = 62.5.

So theoretically 62 74LS00 is the absolute maximum before you break the IO pin.