PCF8574T I/O Expander[FAQ+Video]: Datasheet, Alternatives, and Circuit

The PCF8574T IO Expansion Board is used as a remote 8-bit I/O expander for I2C-bus. Up to 8 PCF8574, T IO Expansion Board can be connected to the I2C-bus, providing up to 64 I/O ports.

The PCF8574T IO Expansion Board features allow the use of multi modules connected to the I2C bus at the same time by connecting the pin header and connector.

There is a small potentiometer on board, which can adjust the backlight of LCD1602 or LCD2004, and a jumper cap to control the switch of the LED light.

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3D Models

NXP USA Inc. PCF8574T/3,512 technical specifications, attributes, parameters and parts with similar specifications to NXP USA Inc. PCF8574T/3,512.

• 2C-bus to the parallel port expander

• 100 kHz I2C-bus interface (Standard-mode I2C-bus)

• Operating supply voltage 2.5 V to 6 V with non-overvoltage tolerant I/O held to VDD with 100 mA current source

• 8-bit remote I/O pins that default to inputs at power-up

• Latched outputs directly drive LEDs

• Total package sink capability of 80 mA

• The active LOW open-drain interrupt output

• Eight programmable slave addresses using three address pins

• Low standby current (2.5 mA typical)

• -40 ℃ to +85 ℃ operation

• ESD protection exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per JESD22-C101

• Latch-up testing is done to JEDEC Standard JESD78 which exceeds 100 mA

• Packages offered: DIP16, SO16, SSOP20

he example circuit diagram is shown in the image below.

• The main component of the I2C LCD display is the PCF8574 I/O expander, with only two pins SDA and SCL we get a maximum of 8 pins from P0 to P7. PCF8574A also can be used but it has a different address.

• All LCD data pins are connected to the PCF8574 where: RS, RW, E, D4, D5, D6, and D7 are connected to P0, P1, P2, P4, P5, P6, and P7 respectively.

• PCF8574 I/O expander SDA and SCL pins are connected to Arduino pins A4 and A5 respectively (Arduino SDA and SCL pins).

• PCF8574 I/O expander A0, A1, and A2 pins are the address pins that decide the I2C address of the chip. In this example, each pin is connected to +5V through a 10k ohm resistor (the 10k resistor is optional, each pin can be connected directly to +5V).

• The I2C address of the PCF8574 is: 0x20 | A2 A1 A0 ( | means OR)

• In our circuit A2, A1 and A0 are connected to +5V (through 10k resistors) which means the I2C address is equal to 0x20 | 7 = 0x27

• If the PCF8574A is used instead of the PCF8574 the I2C address is: 0x38 | 7 = 0x3F.

NXP Semiconductors N.V. (NXP) is a Dutch semiconductor designer and manufacturer with headquarters in Eindhoven, Netherlands. The company employs approximately 29,000 people in more than 30 countries. NXP reported revenue of $11.06 billion in 2021.

Originally spun off from Philips in 2006, NXP completed its initial public offering, on August 6, 2010, with shares trading on NASDAQ under the ticker symbol NXPI. On December 23, 2013, NXP Semiconductors was added to the NASDAQ 100. On March 2, 2015, it was announced that NXP would merge with Freescale Semiconductor. The merger was closed on December 7, 2015. On October 27, 2016, it was announced that Qualcomm would try to buy NXP. Because the Chinese merger authority did not approve the acquisition before the deadline set by Qualcomm, the attempt was effectively canceled on July 26, 2018.