NXP PCA8574D,518 Remote 8-bit I/O Expander for I2C Bus

The NXP PCA8574D,518 is a highly versatile remote 8-bit I/O expander designed to operate on the I²C bus interface. This compact integrated circuit (IC) provides a simple solution for expanding input/output capabilities when microcontroller I/O pin resources are limited. The PCA8574D,518 is particularly suitable for applications where remote I/Os are required, making it an ideal choice for a wide range of industrial, automotive, and consumer electronics.

With its 8-bit quasi-bidirectional I/O port, the PCA8574D,518 allows easy serial expansion of I/O through a two-wire bidirectional bus (I²C). The device consists of an 8-bit quasi-bidirectional port and an I²C-bus interface. The port can be actively driven as either an input or an output and is configured via the I²C-bus. This means that each bit can be used as an input or output without the use of a data direction control signal. This feature significantly simplifies the host controller software architecture and saves I/O lines for other uses.

Each I/O port of the PCA8574D,518 can be configured to a high-impedance input or a strong pull-up/pull-down output, providing flexible host control. The system designer can thus optimize the I/O port configuration to match the required application. Additionally, the IC features an interrupt output that can be connected to the interrupt logic of the microcontroller. This interrupt output is activated when any input state differs from its corresponding input port register state and is used to indicate to the host controller that an input state has changed.

The PCA8574D,518 operates over a wide power supply range (2.5V to 6V) and supports clock frequencies up to 400 kHz (Fast-mode I²C). Its low standby current consumption makes it suitable for battery-powered applications. The device comes in a small 16-pin SO package, which is ideal for space-constrained applications.

In summary, the NXP PCA8574D,518 offers a cost-effective, simple, and efficient way to increase the I/O capabilities of microcontroller-based systems with minimal pin count and power consumption.