TCA9537 Remote 4-Bit I²C & SMBus I/O Expander Texas Instruments TCA9537 Remote 4-Bit I2C and SMBus I/O Expander offers a 1.65V to 5.5V VCC operation and general-purpose remote I/O expansion via the I²C interface. 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 stored in the corresponding input or output register. The polarity of the Input Port register can be inverted with the Polarity Inversion register.