The CA9535 is a 16-bit I²C/SMBus I/O expander designed to provide remote GPIO expansion for a wide range of MCU-based systems. It integrates two 8-bit input port registers, output port registers, configuration registers and polarity inversion registers, allowing each pin to be individually configured as an input or output. At power-up, all 16 I/O pins default to inputs without internal pull-up resistors.

The device features low standby current, 5.5 V tolerant I/Os, and an open-drain interrupt output that notifies the host when an input state changes. A built-in power-on reset ensures proper initialization, while the output latch function supports direct LED driving with higher current capability. With support for I²C speeds up to 1 MHz and up to eight slave addresses, the CA9535 is ideal for server, notebook and telecom applications where flexible and efficient GPIO expansion is required.