The PCA8574/74A devices provide general-purpose remote I/O expansion via the two-wire bidirectional I²C‑bus (serial clock (SCL), serial data (SDA)). They consist of eight quasi-bidirectional ports, 400 kHz I²C‑bus interface, three hardware address inputs and interrupt output operating between 2.3 V and 5.5 V. The system master can read from the input port or write to the output port through a single register.
Except for the different fixed portion of the slave address, the PCA8574 and PCA8574A are identical. The three hardware address pins allow eight of each device to be on the same I²C‑bus, so there can be up to 16 of these I/O expanders PCA8574/74A together on the same I²C‑bus, supporting up to 128 I/Os (for example, 128 LEDs).
- Operating supply voltage 2.3 V to 5.5 V with 5.5 V tolerant I/Os held to VDD with 100 μA current source
- Latched outputs with 25 mA sink capability for directly driving LEDs
- Total package sink capability of 200 m
- Active LOW open-drain interrupt output
- SD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per JESD22-C101
- LED signs and displays
- Key pads
- Industrial control
- Medical equipment