PCAL9539AHF,128 is a low-voltage 16bit general purpose input/output (GPIO) expander with interrupt and reset for I²C-bus/SMBus applications. NXP I/O expander provides a simple solution when additional I/Os are needed while keeping interconnections to a minimum, for example, in ACPI power switches, sensors, push buttons, LEDs, fan control, etc. In addition to providing a flexible set of GPIOs, the wide VDD range of 1.65V to 5.5V allows them to interface with next-generation microprocessors and microcontrollers where supply levels are dropping down to conserve power. The PCAL9539A contains the PCA9539 register set of four pairs of 8-bit configuration, input, output, and Polarity inversion registers, and additionally, the PCAL9539A has Agile I/O, which are additional features specifically designed to enhance the I/O.