PCF8574 Remote 8-Bit IO Expander for I2C Bus

The PC8574 is an 8-bit input/output (I/O) expander for the two-line bidirectional bus (I2C) designed for 2.5-V to 6-V VCC operation. The PCF8574 device provides general-purpose remote I/O expansion for most microcontroller families by way of the I2C interface [serial clock (SCL), serial data (SDA)].

 

PC8574 Pinout Configuration

Pin Number	Pin Name	Description
1	A0	Set Address inputs 0
2	A2	Set Address inputs 1
3	A2	Set Address inputs 2
4	P0	Push-Pull I/O Port 0
5	P1	Push-Pull I/O Port 1
6	P2	Push-Pull I/O Port 2
7	P3	Push-Pull I/O Port 3
8	GND	Ground
9	P4	Push-Pull I/O Port 4
10	P5	Push-Pull I/O Port 5
11	P6	Push-Pull I/O Port 6
12	P7	Push-Pull I/O Port 7
13	INT	Interrupt Output Active High
14	SCL	Serial Clock Line
15	SDA	Serial Data Line
16	VCC	Supply Voltage

 

Features & Specifications

• Low Standby-Current Consumption of 10 μA Max
• I 2C to Parallel-Port Expander
• Open-Drain Interrupt Output
• Compatible with Most Microcontrollers
• Latched Outputs with High-Current Drive Capability for Directly Driving LEDs
• Latch-Up Performance Exceeds 100 mA Per JESD 78, Class II

 

Note: Complete technical details can be found in the PCF8574 IC datasheet given at the end of this page.

 

PCF8574 Equivalent ICs

XIO3130INMH, TIOS101DMWT, TIOL1115DMWT

 

Brief Introduction to PCF8574 IO Expander IC

The PCF8574 is an 8-bit input/output (I/O) expander for the two-line bidirectional bus (I2C) is designed for 2.5-V to 6-V VCC operation.

The device features an 8-bit quasi-bidirectional I/O port (P0–P7), including latched outputs with high current drive capability for directly driving LEDs. Each quasi-bidirectional I/O can be used as an input or output without the use of a data-direction control signal. At power-on, the I/Os are high. In this mode, only a current source to VCC is active.

This device has a wide input voltage range and it can operate in a range of between 2.5V to 7V, the input current range is 20mA and the continuous output current is 4mA and this device can operate in between the range of 150*C. This device has support for both high speed and low-speed SPI that means this device can operate at 100KHz

 

How to Use PCF8574 IO Expander IC

The PCF8574 is a very basic IC and it’s very easy to use, if you are designing your own board with this IC, you need to care only for two things, first is that the A0, A1, and A2 pins sets up the I2C address so you need to look at the following table in the datasheet to know your address and plane accordingly, a screenshot of the table is shown below

Next, you need to add pull-up resistors in every other pin on this IC because the output of this IC is open drain configured so you need to add pull-up resistors in order to work with them. A typical example schematic of this device is shown below,

In the next part, we will learn how to use the I2C interface, in order to work with I2C you need to understand three things first is the Parameter Measurement Information which is not that super important because the I2C handwear take careers of it by itself, 

Next is the timing diagram for the address and data those have read and write mode, the timing diagram for the read mode is shown below,

And in the timing diagram below we see the setup for the write mode,

 

Applications

• Telecom Shelters: Filter Units
• Servers
• Routers (Telecom Switching Equipment)
• Personal Computers
• Personal Electronics
• Industrial Automation
• Products with GPIO-Limited Processors

 

2D Model and Dimensions

If you are designing a PCB or Perf board with this component, then the following picture from the Datasheet will be useful to know its package type and dimensions.