TCA9534A Low-Power I/O Expander Texas Instruments TCA9534A Low-Power I/O Expander provides 8 bits of general purpose parallel input and output (I/O) expansion for the two-line bidirectional I2C bus (or SMBus) protocol. The TCA9534A can operate with a power supply voltage ranging from 1.65V to 5.5V. This voltage range allows for use with a wide range of devices. The device supports 100kHz (Standard-mode) and 400kHz (Fast-mode) clock frequencies. I/O expanders such as the TCA9534A provide a simple solution when additional I/Os are needed for switches, sensors, pushbuttons, LEDs, fans, and other similar devices. The features of the TCA9534A include an interrupt that is generated on the INT pin. This interrupt allows the master to know when an input port changes state. The A0, A1, and A2 hardware selectable address pins allow up to eight devices on the same I2C bus. The device can also be reset to its default state by cycling the power supply and causing a power-on reset.