PCF8574T/3,512

I/o Expanders Overview

The PCF8574T/3,512 is an 8-bit remote I/O expander for the I²C-bus with interrupt. It provides general-purpose remote I/O expansion via the two-wire bidirectional I²C-bus (serial clock SCL, serial data SDA). The device consists of eight quasi-bidirectional ports, a 100 kHz I²C-bus interface, three hardware address inputs, and an interrupt output operating between 2.5 V and 6 V. The quasi-bidirectional port can be independently assigned as an input to monitor interrupt status or keypads, or as an output to activate indicator devices such as LEDs. System master can read from the input port or write to the output port through a single register. The low current consumption of 2.5 µA (typical, static) is great for mobile applications and the latched output ports directly drive LEDs.

I/o Expanders Feature Summary

• I2C-bus to parallel port expander
• Active LOW open-drain interrupt output
• Eight programmable slave addresses using three address pins
• Low standby current

I/o Expanders Applications

• LED signs and displays
• Servers
• Key pads
• Industrial control
• Medical equipment

I/o Expanders Procurement Notes

Verify the specific ordering suffix /3,512 against the manufacturer's official documentation to confirm the SO16 package type and tube dry pack configuration. Ensure that the fixed portion of the slave address corresponds to the PCF8574 variant rather than the PCF8574A variant, as these are functionally identical but possess different fixed address bits.

I/o Expanders Selection Notes

Select this component when designing systems requiring remote I/O expansion over the standard-mode I2C bus. It is suitable for applications needing up to eight additional digital I/O lines controlled by a microcontroller. Consider the quasi-bidirectional nature of the ports and the requirement for external pull-ups if high-level driving capability is needed beyond the internal weak current source.

I/o Expanders Part Context

This part belongs to the PCF8574 family of remote I/O expanders. It shares functional similarities with the PCF8574A, differing primarily in the fixed portion of the slave address. This allows both variants to coexist on the same I2C bus, supporting up to sixteen devices total. Newer replacements like the PCA9674 offer higher speeds and more addresses.

I/o Expanders Replacement Considerations

Public confirmed substitute part numbers include PCA8574 and PCA9674. These newer components offer higher I2C frequencies and increased address capabilities while maintaining drop-in compatibility in terms of pinout and basic functionality.