Dual 1-of-4 decoder — what it does on the board
The SN74HC139QDRQ1 is a dual 1-of-4 decoder/demultiplexer in the 74HC logic family, qualified to AEC-Q100 for automotive use. Each of the two independent circuits takes a 2-bit address input and asserts one of four active-low outputs.
Automotive temperature range and package
Surface-mount only; no through-hole variant in this qualification grade.
What the output current rating means for your BOM
The 5.2 mA per output (both high and low) is typical for HC logic. It will directly drive CMOS inputs, a microcontroller pin, or a low-current indicator.