The PCA9536 is an 8-pin CMOS device that provides 4 bits of General Purpose parallel Input/Output (GPIO) expansion for I2C-bus/SMBus applications and was developed to enhance the NXP Semiconductors family of I2C-bus I/O expanders. I/O expanders provide a simple solution when additional I/O is needed for ACPI power switches, sensors, push buttons, LEDs, fans, etc.