The TCA9538 is a 16-pin device that provides 8 bits of general purpose parallel input and output (I/O) expansion for the two-line bidirectional I2C bus (or SMBus) protocol. The device can operate with a power supply voltage ranging from 1.65 V to 5.5 V. The device supports both 100-kHz (Standard-mode) and 400-kHz (Fast-mode) clock frequencies. I/O expanders such as the TCA9538 provide a simple solution when additional I/Os are needed for switches, sensors, push-buttons, LEDs, fans, etc. The features of the TCA9538 include an interrupt that is generated on the INT pin whenever an input port changes state. The A0 and A1 hardware selectable address pins allow up to four TCA9538 devices on the same I2C bus. The device can also be reset to its default sate by using the RESET feature or by cycling the power supply and causing a power-on reset.