The PCA9536 device is a 4-bit I/O expander for the I²C bus and is designed for 1.65-V to 5.5-V V_CC operation. It provides general-purpose remote I/O expansion for most microcontroller families through the I²C interface.

The PCA9536 consists of a configuration (input or output selection), Input Port, Output Port, and Polarity Inversion (active-high or active-low operation) registers. At power-on, the I/Os are configured as inputs. The system controller enables the I/Os as either inputs or outputs by writing to the I/O configuration register bits. The data for each input or output is kept in the corresponding input or output register. The polarity of the Input Port register can be inverted with the Polarity Inversion register and the system controller reads all registers.

The device outputs (latched) have high-current drive capability for directly driving LEDs.