This 4-bit I/O expander for the two-line bidirectional bus (I²C) is designed for 2.3-V to 5.5-V V_CC operation. It provides general-purpose remote I/O expansion for most microcontroller families via the I²C interface [serial clock (SCL), serial data (SDA)].

The PCA9536 features 4-bit Configuration (input or output selection), Input Port, Output Port, and Polarity Inversion (active high or active low) registers. At power on, the I/Os are configured as inputs with a weak pullup to V_CC. However, the system master can enable the I/Os as either inputs or outputs by writing to the I/O configuration bits. If no signals are applied externally to the PCA9536, the voltage level is 1, or high, because of the internal pullup resistors. The data for each input or output is stored in the corresponding Input Port or Output Port register. The polarity of the Input Port register can be inverted with the Polarity Inversion register. All registers can be read by the system master.

The system master can reset the PCA9536 in the event of a timeout or other improper operation by utilizing the power-on reset feature, which puts the registers in their default state and initializes the I²C/SMBus state machine.

The device's outputs (latched) have high-current drive capability for directly driving LEDs. It has low current consumption.