Octal inverting bus transceiver — active 74LS logic
The SN74LS640-1DW is an octal (8-bit) inverting bus transceiver from the 74LS logic family. It provides bidirectional data flow between two buses with 3-state outputs, and the data is inverted at each direction.
The output drive is rated 15 mA high-level and 48 mA low-level. That 48 mA sink capability is typical of 74LS and gives you solid fan-out to multiple LSTTL loads or a terminated backplane. The 15 mA source is modest — plan for it when driving LED indicators or long traces without a pull-up.
Fine for office equipment, appliances, test gear, and rack-mounted telecom that stays climate-controlled.
20-SOIC footprint — wide-body surface mount
Packaged in a 20-SOIC wide-body (7.50 mm width) case. The wide body gives better thermal dissipation than the narrow SOIC for the same pin count. Surface-mount only — no through-hole version of this exact code.
Listed as Active in the product lifecycle. This is a current-production part, not a phase-out. No second-source listed in the official cross-reference, but the 74LS family is widely second-sourced by multiple manufacturers — verify pin-compatibility with your specific alternate.