NXP Semiconductors PCF8574AP,112

Overview

PCF8574AP,112 from NXP Semiconductors is an 8-bit quasi-bidirectional I²C-bus I/O expander with active-low open-drain interrupt output, operating from 2.5 V to 6 V, supporting 100 kHz Standard-mode I²C communication, and featuring 8 latched I/O ports that default to inputs with 100 µA internal pull-up at power-on - used in LED signage, keypad scanning, and industrial control interfaces.

For engineers reviewing the PCF8574AP,112 datasheet, PCF8574AP,112 pinout, PCF8574AP,112 application, or PCF8574AP,112 equivalent, this device delivers remote parallel I/O expansion with low standby current (2.5 µA typical), hardware-addressable slave addressing (3 pins → 8 options), and interrupt-driven input change detection - critical for minimizing microcontroller polling overhead in embedded systems.

Technical Context

The PCF8574AP,112 implements a single-register quasi-bidirectional I/O architecture: each of P0–P7 functions as input or output without direction register, controlled by write-to-register state and external voltage level. Its interrupt logic asserts INT (active LOW) on any input state transition relative to the port register, resetting upon read or write access.

It uses an internal Power-On Reset (POR) circuit that initializes all I/Os as HIGH inputs with 100 µA weak pull-up; no external reset required. The I²C interface complies strictly with Standard-mode (100 kHz), and address resolution relies solely on A0–A2 pins - fixed slave address prefix 0x70–0x77 (hex write) for PCF8574A variant, distinct from PCF8574's 0x40–0x47 range.

Key Specifications

Pinout & Package

DIP16 plastic dual in-line package (300 mil), through-hole mount, compatible with standard 0.1″ pitch PCB layouts and manual soldering workflows.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C I/O expander applications.

Compared with PCF8574AP,112, PCA8574AP,118 offers faster I²C throughput and lower voltage operation but sacrifices 6 V tolerance, while PCA9674APW,118 adds address scalability and speed at the cost of reduced minimum supply voltage - both require validation of VDD range and timing constraints in existing designs.

Availability

PCF8574AP,112 is available at Aetrix Electronics and suitable for industrial control, LED signage, and keypad interface applications requiring stable component supply, long-term lifecycle support, and traceable sourcing from authorized channels.

Supply support for PCF8574AP,112 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in interface, power management, and microcontroller technologies.

The PCF8574AP,112 belongs to NXP's legacy I²C I/O expander product line, designed specifically for cost-sensitive, space-constrained embedded systems needing simple, reliable parallel I/O extension over two-wire buses.

FAQ

What is the I²C slave address range for PCF8574AP,112?

The PCF8574AP,112 uses the PCF8574A address prefix (0x70–0x77 for write, 0x71–0x7F for read), determined by A0–A2 pin states. This differs from PCF8574P,112 (0x40–0x47), allowing both families to coexist on the same I²C bus - up to 16 devices total. Address decoding is purely hardware-based; no software configuration is needed.

How does the quasi-bidirectional I/O work on PCF8574AP,112?

Each P0–P7 pin on PCF8574AP,112 operates as quasi-bidirectional: writing '1' configures it as input with 100 µA pull-up; writing '0' activates a strong sink transistor. No direction register is required. Input reads reflect actual pin voltage; output writes drive LOW actively or HIGH weakly - ideal for LED anode connections and switch sensing without external components.

Can PCF8574AP,112 drive LEDs directly?

Yes - PCF8574AP,112 can directly drive LEDs with cathodes connected to P0–P7 and anodes tied to VDD via current-limiting resistors. Each pin sinks up to 10 mA (80 mA total package limit), and the 100 µA pull-up ensures safe HIGH state when inactive. This eliminates external driver transistors in low-current indicator applications.

What happens to the INT pin when an input changes on PCF8574AP,112?

The INT pin on PCF8574AP,112 goes LOW (active) whenever any P0–P7 input state differs from its corresponding bit in the port register - including power-on reset (where all pins default HIGH). INT resets to HIGH automatically after a read or write access to the port register, enabling edge-triggered interrupt handling without software clearing.

Is PCF8574AP,112 compatible with 3.3 V microcontrollers?

Yes - PCF8574AP,112 operates from 2.5 V to 6 V, making it fully compatible with 3.3 V systems. Its I²C interface meets Standard-mode specifications, and input thresholds (VIH = 0.7×VDD, VIL = 0.3×VDD) ensure reliable communication with 3.3 V MCUs. External pull-ups should match the bus VDD (e.g., 3.3 kΩ @ 3.3 V).