PCF8574N

I/o Expanders Overview

The PCF8574N is an 8-bit I/O expander for the two-line bidirectional I2C bus, designed for operation with a supply voltage range of 2.5V to 6V. It provides general-purpose remote I/O expansion via serial clock (SCL) and serial data (SDA) pins. The device features an 8-bit quasi-bidirectional I/O port (P0–P7) with latched outputs capable of directly driving LEDs. Each I/O can function as input or output without a data-direction control signal. At power-on, the I/Os are high, activating only a current source to VCC. The component operates within a temperature range of -40°C to 85°C and utilizes a 16-pin PDIP package.

I/o Expanders Feature Summary

• I2C to parallel-port expander functionality
• Open-drain interrupt output capability
• Latched outputs with high-current drive capability for directly driving LEDs
• Latch-up performance exceeding 100mA per JESD 78, Class II

I/o Expanders Applications

• Telecom shelters: filter units
• Servers
• Routers (telecom switching equipment)
• Personal computers
• Products with GPIO-limited processors

I/o Expanders Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation to confirm package type and environmental compliance. Ensure the selected variant matches the required thermal and electrical specifications for the target application environment. Cross-reference part numbers with authorized distributors to confirm authenticity and availability status prior to procurement.

I/o Expanders Selection Notes

Select this component when expanding GPIO capabilities for microcontrollers using the I2C interface. Consider the 2.5V to 6V operating voltage range and the 8-bit quasi-bidirectional port configuration. Evaluate the need for open-drain interrupt outputs and the specific drive requirements for connected peripherals like LEDs. Confirm compatibility with the host system's I2C bus timing and address configuration constraints.

I/o Expanders Part Context

The PCF8574 belongs to the PCF8574 series of remote 8-bit I/O expanders for the I2C bus. This family includes variants such as PCF8574AN, PCF8574AP, PCF8574AW, PCF8574BPN, PCF8574BPW, PCF8574DGV, PCF8574DGVR, PCF8574DW, PCF8574DWG4, PCF8574DR, PCF8574DRG4, PCF8574DT, PCF8574DTG4, PCF8574N, PCF8574NE4, PCF8574PW, PCF8574PWG4, PCF8574RGY, and PCF8574RGYG4.

I/o Expanders Replacement Considerations

PCF8574NE4 is a verified equivalent part number for the PCF8574N.

I/o Expanders FAQ

How does the PCF8574 handle interrupt generation?

An interrupt is generated by any rising or falling edge of the port inputs in the input mode. The open-drain INT output signals the microcontroller, which resets the interrupt circuit when data on the port is changed to the original setting or when data is read from or written to the port.

What is the state of the I/O ports at power-on?

At power-on, the I/Os are high. In this mode, only a current source to VCC is active.

Can the I/O ports be used as both inputs and outputs simultaneously?

Yes, each quasi-bidirectional I/O can be used as an input or output without the use of a data-direction control signal.