16 GPIO over two wires
The PCA9539DW is a 16-bit I²C/SMBus I/O expander from Texas Instruments in a 24-SOIC package. It adds 16 push-pull GPIOs to a host controller using just two bus lines (SDA/SCL) plus an interrupt output (INT) that signals a pin-change event without polling.
Drive and board-fit
The push-pull output eliminates the need for external pull-ups on the port pins. The POR (power-on reset) feature ensures the outputs default to a known state (all inputs) when VCC crosses the threshold, so the expander starts clean on every power-up. The tube packaging means it ships in anti-static tubes, not tape-and-reel — plan for hand-placement or tube-fed pick-and-place if your line supports it.