PCA8574AD,512

I/o Expanders Overview

The PCA8574AD,512 is an 8-bit I/O expander for the I2C-bus in a SOIC-16 package. It operates between 2.3 V and 5.5 V with a 400 kHz Fast-mode interface. The device features eight quasi-bidirectional ports that default to inputs at power-up, latched outputs with 25 mA sink capability, and an active LOW open-drain interrupt output. Three hardware address pins allow up to eight devices on one bus. It provides low standby current of 4.5 µA typical and functions within -40 °C to +85 °C.

I/o Expanders Feature Summary

• Provides remote I/O expansion via a two-wire bidirectional I2C-bus interface
• Features eight quasi-bidirectional ports with latched outputs capable of directly driving LEDs
• Includes an active LOW open-drain interrupt output to notify microcontrollers of input state changes
• Supports eight programmable slave addresses using three hardware address pins

I/o Expanders Applications

• LED signs and displays
• Key pads
• Industrial control systems
• PLCs
• Mobile devices

I/o Expanders Procurement Notes

Verify the specific ordering suffix ',512' against official NXP documentation to confirm tube packaging requirements. Ensure the selected variant matches the required operating temperature range and voltage specifications for your application design.

I/o Expanders Selection Notes

Select this component when a drop-in replacement for the PCF8574AD is needed with improved drive capabilities. Consider the PCA8574A variant if a different fixed portion of the slave address is required to prevent conflicts on the same I2C bus alongside standard PCA8574 devices.

I/o Expanders Part Context

This part belongs to the PCA8574/74A family of remote 8-bit I/O expanders. It serves as a direct upgrade to the older PCF8574 series, offering higher speed (400 kHz vs 100 kHz) and significantly increased output sink current (25 mA per pin vs 80 mA total). It maintains pin compatibility while expanding system capacity.

I/o Expanders Replacement Considerations

Officially documented as a drop-in replacement for PCF8574AD. For migration paths, consider the PCA9674 or PCA9670 for higher speed and additional reset functionality.

I/o Expanders FAQ

How does the PCA8574 handle input states?

At power-on, all ports are set to inputs with a weak internal pull-up. To read an external signal, the master must write a logic 1 to the corresponding register bit to disable the strong pull-down transistor.

What is the maximum current sink capability?

Each individual port pin can sink up to 25 mA. The total package sink capability is limited to 200 mA.

How many devices can be connected to a single I2C bus?

Up to eight PCA8574 devices and eight PCA8574A devices can be connected simultaneously, supporting up to 16 devices total by utilizing the three hardware address pins.