PCF8575PWR 16-bit I/O I2C expander TSSOP24

Description

Overview

The PCF8575PWR from Texas Instruments is a 16-bit remote I/O expander that adds 16 general-purpose digital I/O lines to a microcontroller through a simple I²C/SMBus interface. It is designed for applications where additional GPIO pins are required without using more MCU pins.

The device operates from 2.5 V to 5.5 V, supports I²C communication up to 400 kHz, and provides an interrupt output for detecting changes on the input ports. Up to eight PCF8575 devices can share the same I²C bus using the three hardware address pins.

Key Features

• 16-bit GPIO expansion
• I²C / SMBus interface
• Up to 400 kHz I²C bus speed
• Operating voltage: 2.5–5.5 V
• 8 selectable I²C addresses
• Open-drain interrupt output
• Quasi-bidirectional I/O architecture
• No separate direction registers required
• Latched outputs
• Suitable for directly driving LEDs
• Low standby current
• Compact TSSOP-24 package
• −40°C to +85°C operating temperature range

Technical Specifications

TI currently lists PCF8575PWR as an active part number in the 24-pin TSSOP package.

I/O Configuration

The 16 GPIOs are organized into two 8-bit ports:

• P00–P07
• P10–P17

The PCF8575 uses a quasi-bidirectional I/O architecture, allowing each pin to function as either an input or output without a conventional direction-control register. After power-on, the I/O pins are HIGH.

I²C Addressing

Three hardware address pins provide 8 possible I²C addresses, allowing multiple PCF8575 devices to operate on the same I²C bus.

This makes it possible to expand a system by up to 128 additional I/O pins using eight devices, subject to bus loading and system design considerations.

Interrupt

The INT output is an open-drain interrupt signal that can notify the host MCU when an input state changes. This can reduce the need for continuously polling all 16 inputs.

Pin Configuration

Verify the pin numbering against the TI datasheet when creating the PCB footprint or assembly documentation.

Power & Programming

• Supply voltage: 2.5–5.5 V
• Typical applications include 3.3 V and 5 V systems.
• No programming is required.
• The device is controlled through the I²C interface.
• External pull-up resistors are required for the I²C SDA and SCL lines.
• The INT output is open-drain and normally requires a pull-up resistor when used.

Applications

• GPIO expansion for microcontrollers
• Arduino projects
• ESP32 and ESP8266 projects
• STM32 applications
• Relay and LED control
• Keypad and button interfaces
• LCD and display control
• Industrial control systems
• Robotics
• Embedded systems
• I²C-based peripheral expansion

What’s Included

• 1 × Texas Instruments PCF8575PWR 16-Bit I²C I/O Expander IC
• Package: TSSOP-24
• Surface-mount component

Notes

• PCF8575PWR is the active TSSOP-24 version. The older PCF8575PW ordering code is obsolete and has been replaced by PCF8575PWR.
• The PCF8575 is different from the PCF8574, which provides only 8 I/O pins.
• The I/O pins are not equivalent to standard push-pull GPIOs in every operating condition because the PCF8575 uses a quasi-bidirectional architecture.
• When driving loads such as relays, motors, or other high-current devices, use an appropriate transistor, MOSFET, driver IC, or relay-driver circuit rather than connecting the load directly to the PCF8575.
• TSSOP-24 (PW) is the correct package designation for PCF8575PWR.