The Texas Instruments SN74HC258DR is a 74HC-family 4 x 2:1 multiplexer that selects one of two 4-bit data sources onto a single 4-bit output bus. It runs from a single supply between 2V and 6V, making it a drop-in for both 3.3V and 5V logic domains without a level translator. The 16-SOIC package (0.154" body width, 3.90mm) is the standard SOIC-16 footprint used across the 74HC logic family, so the board layout is interchangeable with other 74HCxxx parts in the same package. The 7.8mA sink/source output current is typical for the 74HC family at 5V; it drives one or two standard CMOS loads directly but needs a buffer for heavier fan-out or long backplane traces.
The 2V to 6V supply range means this mux works with 5V TTL/CMOS logic and also with 3.3V systems — no separate regulator or level shifter for the mux itself. At 5V the input thresholds are 0.8V low / 2.0V high, so it reads 3.3V outputs as a valid high. At 3.3V supply the thresholds scale proportionally, and the 7.8mA output current drops slightly but still drives a single 3.3V CMOS load.