PCA8574AD,518

I/o Expanders Overview

The PCA8574AD,518 is an 8-bit remote I/O expander for the I2C-bus with interrupt functionality. It operates within a supply voltage range of 2.3 V to 5.5 V and supports Fast-mode I2C communication at up to 400 kHz. The device features eight quasi-bidirectional ports that default to inputs upon power-up, utilizing a weak internal pull-up current source of 100 µA. Latched outputs provide a high current sink capability of 25 mA per pin, with a total package sink limit of 200 mA. An active LOW open-drain interrupt output signals input state changes to the microcontroller. The component is housed in an SO16 plastic small outline package (SOT162-1) and functions across an ambient temperature range of -40 °C to +85 °C.

I/o Expanders Feature Summary

• Provides general-purpose remote I/O expansion via a two-wire bidirectional I2C-bus interface.
• Features latched outputs with 25 mA sink capability suitable for directly driving LEDs.
• Includes an active LOW open-drain interrupt output to notify the microcontroller of input state changes without continuous polling.
• Supports eight programmable slave addresses using three hardware address pins.

I/o Expanders Applications

• LED signs and displays
• Industrial control systems
• Key pads
• Medical equipment
• PLCs

I/o Expanders Procurement Notes

Verify the specific ordering suffix ',518' corresponds to the reel packing method as defined in the manufacturer's documentation. Confirm the package version matches the SO16 specification (SOT162-1). Ensure the design utilizes the correct fixed portion of the slave address associated with the 'PCA8574' variant rather than the 'PCA8574A' variant to prevent bus conflicts.

I/o Expanders Selection Notes

Select this component when a drop-in replacement for the PCF8574AT/3 is required. Note that while functionally similar to the PCF8574 series, the PCA8574 operates on a different voltage range (2.3 V to 5.5 V) and offers higher current drive capabilities (25 mA vs 80 mA total package limit). Verify that the system I2C bus speed requirements align with the 400 kHz Fast-mode support.

I/o Expanders Part Context

This part belongs to the PCA8574 family of remote 8-bit I/O expanders designed for I2C-bus applications. It serves as a direct functional upgrade to the older PCF8574 series, offering improved current sinking capabilities and operation at lower voltages. The 'AD' designation indicates the specific device variant (PCA8574) packaged in the SO16 format.

I/o Expanders Replacement Considerations

The datasheet explicitly identifies the PCA8574D as a drop-in replacement for the PCF8574T/3. Consequently, the PCA8574AD serves as the equivalent replacement for the PCF8574AT/3. Designers migrating from the PCF8574 series should account for the differences in operating voltage and I2C bus frequency specifications.