The PCA9554DBR is an 8-bit I²C/SMBus I/O expander from Texas Instruments that adds eight general-purpose I/O pins to a microcontroller via a two-wire serial bus. The I²C interface operates up to 400 kHz (fast-mode), and the push-pull outputs can source 10 mA or sink 25 mA per pin, enough to drive LEDs or small relays with external resistors.
16-SSOP — rework and layout notes
The 16-SSOP package (5.30 mm body width, 0.209" pitch) is a standard fine-pitch SOIC variant. It reflows well with a typical leaded profile; the 1.27 mm pitch leaves room for manual touch-up if needed. The POR (power-on reset) feature ensures the outputs default to a known state at power-up, which simplifies the firmware bring-up sequence.