Octal bus transceiver for legacy 5V backplanes
The Texas Instruments SN74ALS245A-1N is an octal (8-bit) non-inverting bus transceiver from the 74ALS family, packaged in a 20-pin DIP for through-hole assembly. It provides bidirectional data flow between two 8-bit buses, controlled by direction and output-enable pins. The 3-state outputs allow multiple transceivers to share a common bus without contention.
The output drive is rated 15mA sourcing and 24mA sinking. In a 5V TTL backplane, 24mA sink gives enough margin to drive a standard LSTTL load of eight inputs plus the bus termination. The 15mA source side is lower than later 74ABT or 74LVTH families, so if the bus has many pull-up resistors or long trace capacitance, check the high-level noise margin at the far end.
Package and fit
The 20-pin DIP (0.300" body width) is the standard legacy footprint — same as a 20-pin DIP socket. The 74ALS245A-1N variant uses a tighter propagation delay spec than the standard 74ALS245, which matters in timing-critical paths where the 1-NS suffix indicates a faster bin.
Listed as Active product status and ROHS3 compliant. The ROHS3 compliance covers the current exemption set, so it remains acceptable for new designs requiring lead-free assembly.