Texas Instruments

PCF8575PW

PCF8575PW Description

The PCF8575PW from Texas Instruments is a 16-bit I/O expander designed for I2C-bus and SMBus applications, providing a simple solution for interfacing microcontrollers with additional digital I/O ports. Operating at a clock frequency of 400 kHz, it supports bidirectional data transfer and is optimized for low-voltage (4.5V–5.5V) systems. Housed in a 24-pin TSSOP package, this device is ideal for space-constrained designs. Although marked as obsolete, it remains a reliable choice for legacy systems due to its robust performance and ROHS3 compliance.

PCF8575PW Features

• 16 I/O Ports: Configurable as inputs or outputs with 10mA source/25mA sink capability, enabling direct drive of LEDs or relays.
• I2C/SMBus Interface: Ensures compatibility with standard microcontroller communication protocols.
• Interrupt Output: Minimizes polling overhead by alerting the host controller of input state changes.
• Power-On Reset (POR): Guarantees stable initialization at startup.
• Wide Voltage Range (4.5V–5.5V): Suitable for 5V-dominated systems.
• Surface-Mount (TSSOP) Packaging: Optimized for compact PCB layouts.

PCF8575PW Applications

The PCF8575PW excels in scenarios requiring I/O expansion without GPIO pin consumption on the host MCU, such as:

• Industrial Control Systems: For sensor interfacing or actuator control.
• Consumer Electronics: Keypad scanning, LED matrix driving.
• Embedded Systems: Adding peripheral control (e.g., switches, displays) to resource-constrained microcontrollers.
• Automotive Modules: Non-critical signal conditioning where 5V logic is prevalent.

Conclusion of PCF8575PW

While obsolete, the PCF8575PW offers a proven, cost-effective solution for I2C-based I/O expansion with features like high sink current, interrupt support, and compact packaging. Its 400 kHz operation ensures responsive performance in multi-device bus configurations. Engineers maintaining or designing legacy 5V systems will find it particularly valuable for minimizing MCU resource usage while expanding functionality. For new designs, consider TI’s modern alternatives with enhanced features.