Device identity and logic family
The SN54F251AJ is a multiplexer from the F/FAST series, a bipolar logic family known for its speed. It is supplied in a Bulk package, typical for through-hole DIP components that are ordered in tray or tube quantities for production runs.
This component is RoHS non-compliant, which is a consideration for designs that must meet the EU Restriction of Hazardous Substances directive — legacy or military/avionics BOMs often exempt this requirement.