1:8 addressable latch for bus expansion
The Texas Instruments SN74LS259BDR is an 8-bit addressable latch from the 74LS Schottky-clamped bipolar family, organized as a 1:8 demultiplexer with a standard output type. It takes a single data input and routes it to one of eight output latches selected by the three address lines — useful for expanding a microcontroller's output ports or implementing a serial-to-parallel converter on a low-pin-count bus. The 19ns propagation delay is typical for LS logic and sets the ceiling for the data clock rate: at 5V supply, the output settles within 19ns of the address or data change, so the downstream logic must wait at least that long before strobing the latched data. The 400µA source / 8mA sink output current drives standard LS or HCT inputs directly but will struggle with a heavily loaded bus — plan a buffer if fan-out exceeds ten loads.
Supply and package constraints
The 4.75V to 5.25V supply rail is a tight 5V ±5% — a switching regulator with 1% set-point accuracy is fine, but a 5V rail from a 78L05 regulator with 5% tolerance and load regulation may drift below 4.75V at full load, causing the latch to behave unpredictably.