I/O expansion module
ON Semiconductor

The CAT9554 and CAT9554A are CMOS devices that provide 8-bit parallel input/output port expansion for I²C and SMBus compatible applications. These I/O expanders provide a simple solution in applications where additional I/Os are needed: sensors, power switches, LEDs, pushbuttons, and fans.

The CAT9554/9554A consist of an input port register, an output port register, a configuration register, a polarity inversion register and an I²C/SMBus-compatible serial interface.

Any of the eight I/Os can be configured as an input or output by writing to the configuration register. The system master can invert the CAT9554/9554A input data by writing to the active-high polarity inversion register.

The CAT9554/9554A features an active low interrupt output which indicates to the system master that an input state has changed.

The device's extended addressing capability allows up to 8 devices to share the same bus. The CAT9554A is identical to the CAT9554 except the fixed part of the I²C slave address is different. This allows up to 16 of devices (eight CAT9554 and eight CAT9554A) to be connected on the same bus.