Supply range and drive capability — what the 2V–6V and 24mA ratings mean
The SN74AC240DWR: The 2V to 6V supply span means this buffer works directly with 3.3V and 5V logic families without an external level shifter. The symmetrical 24mA output drive (both high and low) is enough to fan out to ten standard LSTTL loads or drive a short ribbon cable, but not intended for heavy capacitive loads like long backplanes.
The 74AC family's CMOS inputs have good noise immunity across this range, though the 3-state outputs need pull-up or pull-down resistors on the enable lines if the bus floats during power sequencing.
The ROHS3 rating covers the full substance restriction list, so it qualifies for new designs targeting EU and global markets without exemption tracking.