Octal transparent latch with tri-state bus hold
The Texas Instruments SN74AC563N is an octal D-type transparent latch in the 74AC logic family. When the latch-enable input is high, the Q outputs follow the D inputs; when low, the outputs latch the last data. The tri-state output control lets you isolate the latch from the bus, which is useful in shared-data-path designs like microprocessor memory interfaces or I/O port expansion. The 20-pin DIP package (0.300" body width) is a through-hole footprint that suits prototyping, legacy board repairs, or designs where vibration resistance matters more than board density. Industrial temperature range (-40°C to 85°C) covers factory-floor enclosures, outdoor telecom cabinets, and unheated storage.
Lifecycle and sourcing
The SN74AC563N is listed as Active with RoHS3 compliance. No end-of-life notice or last-time-buy schedule is in effect, so it remains a standard catalog item through TI's distribution channel. For BOM planning, this means no near-term requalification risk — you can freeze the line item without watching for a PCN.
Tri-state output: bus isolation without a separate buffer
The tri-state output enable (active-low) lets multiple latches share a common data bus. When the output enable is high, the outputs go high-impedance — the latch still captures data internally, but the bus sees no load. This is the standard architecture for memory address latches, peripheral I/O ports, and bidirectional data buffers where you need to park the outputs during a bus turn-around.