What this 16-bit I²C GPIO expander does
The NXP PCA9555PW is a 16-bit general-purpose I/O expander that connects to an I²C or SMBus host controller using just two wires (SCL, SDA) at up to 400 kHz. Each of the 16 I/O pins can be configured as input or output individually; outputs are push-pull, rated for sourcing 10 mA and sinking 25 mA per pin. A dedicated interrupt output (INT) signals the host when an input changes state, eliminating continuous polling. It is supplied in a 24-TSSOP package (4.40 mm width) for surface-mount assembly.
The 2.3 V minimum supply allows operation on a 3.3 V rail with margin, and the 5.5 V maximum covers legacy 5 V buses without a level shifter.
NXP has marked the PCA9555PW as obsolete. That means it is no longer in production and not available through the authorized factory channel. For a BOM line that calls this exact order code, procurement must turn to independent distribution for new-old-stock or surplus inventory. Every unit we quote is physically verified — date-code consistency and marking integrity checked — because obsolete parts are a prime target for re-marked or re-badged counterfeits.
POR feature and package note
The PCA9555PW includes a Power-On Reset (POR) feature that initializes the internal registers to a known state when the supply voltage rises.