Octal buffer with 64 mA sink — the bus-driving workhorse
The IDT74FCT244TQ is an octal buffer and line driver from Renesas (formerly IDT), built in the FCT logic family. It buffers eight signals with non-inverting pass-through and 3-state outputs, meaning you can tie multiple drivers to the same bus and disable this one without loading the line. The headline spec is the output drive: 15 mA source, 64 mA sink at the output pins.
If your board runs a 5 V rail with ±10 % tolerance, the low end at 4.5 V is below this part's minimum — the regulator needs to hold regulation within 5 %. Two elements of four bits each means the eight channels are split into two independent 4-bit nibbles, each with its own output-enable control. That lets you gate half the bus while the other half drives — handy for byte-wide data paths where you need separate control over the upper and lower nibble.
20-SSOP vs 20-QSOP — two package names, same footprint
These are the same mechanical footprint — the QSOP is the tighter-lead-frame variant of the SSOP body. Either way, the PCB land pattern is a 20-pin SOIC-width body with 0.025" (0.635 mm) pitch. Surface-mount only — no through-hole option.
RoHS non-compliant per the lifecycle record. If your BOM requires RoHS-10 exemption or you are building for a RoHS-exempt market (military, medical implant, some industrial), this part fits. For full RoHS compliance, look at the lead-free suffix variants in the same FCT244 family.