CA9555 is a low-voltage, 16-bit I/O expander for I²C/SMBus applications. It provides two independently configurable 8-bit I/O ports, allowing designers to extend the number of GPIOs available to a host MCU. Each pin can be individually set as input or output through the configuration register, and an additional polarity inversion register enables active-high or active-low input modes.

The device supports standard and Fast-mode I²C communication up to 400 kHz, and its three hardware address pins allow up to eight CA9555 devices to coexist on the same bus. After power-on reset, all pins default to input mode, ensuring a safe initial state during system startup.

Built-in power-on reset, low power consumption, and compatibility with bus voltages up to 5.5 V make the CA9555 well suited for server platforms, telecom hardware, industrial systems, and any design requiring flexible remote GPIO expansion. The device is available in compact TSSOP-24 and QFN4×4-24 packages.