NXP Semiconductors PCA9674D,518

Overview

PCA9674D,518 from NXP Semiconductors is an 8-bit remote I/O expander for Fast-mode Plus (Fm+) I²C-bus with interrupt output, operating from 2.3 V to 5.5 V, featuring 8 quasi-bidirectional I/O ports, 1 MHz I²C interface, 25 mA per-port sink drive for direct LED control, and active-low open-drain INT pin. It is used in industrial control panels to extend microcontroller GPIO for keypad scanning and status LED indication.

For engineers reviewing the PCA9674D,518 datasheet, PCA9674D,518 pinout, PCA9674D,518 application, or PCA9674D,518 equivalent, key selection considerations include its Fm+ I²C compatibility (1 MHz), 25 mA per-port sink capability, 64 programmable slave addresses via AD0–AD2, and latched output behavior with internal 100 µA pull-up at power-on.

Technical Context

The PCA9674D,518 implements a quasi-bidirectional I/O architecture-no direction register required-where each port defaults to input with 100 µA weak pull-up to VDD at power-on. Input state monitoring and output activation are handled through a single 8-bit register accessed via I²C read/write operations.

Its interrupt logic asserts the active-low open-drain INT pin when any input port state differs from its corresponding register value, enabling efficient change-of-state detection without polling. The device supports Software Reset (00h + 06h sequence) and Device ID read (F8h address) for system identification and recovery.

Key Specifications

Pinout & Package

PCA9674D,518 is housed in a 16-pin SOIC (SO16) package (SOT162-1), 7.5 mm body width, standard marking, dry pack reel format. Pin assignments are validated per NXP datasheet Rev. 7 (May 2013).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9674AD,518, the PCA9674D,518 offers broader address flexibility (64 vs. 62 options); versus PCA9672D,518, it adds critical interrupt signaling and 1 MHz I²C for responsive, high-throughput I/O expansion.

Availability

PCA9674D,518 is available at Aetrix Electronics and suitable for industrial control panels, medical equipment UIs, and cellular baseband modules requiring stable component supply across extended product lifecycles.

Supply support for PCA9674D,518 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 company specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9674 family is designed as a robust, low-power I²C I/O expander targeting industrial HMI, server management, and portable electronics needing reliable GPIO extension with interrupt capability.

FAQ

What is the maximum I²C bus speed supported by the PCA9674D,518?

The PCA9674D,518 supports Fast-mode Plus (Fm+) I²C operation up to 1 MHz. This allows significantly faster data transfer than standard Fast-mode (400 kHz), enabling rapid updates for LED dimming or keypad scanning. Its SDA line provides 30 mA sink capability to maintain signal integrity on heavily loaded buses up to 4000 pF, making the PCA9674D,518 suitable for dense multi-device systems without external bus buffers.

How does the quasi-bidirectional I/O architecture of the PCA9674D,518 differ from standard GPIO expanders?

The PCA9674D,518 uses a quasi-bidirectional I/O structure that eliminates the need for a separate direction register. Each port (P0–P7) defaults to input with a 100 µA internal pull-up to VDD at power-on. Writing '1' configures it as input; writing '0' activates a 25 mA sink for output LOW. This simplifies firmware and reduces memory overhead-critical in resource-constrained microcontrollers. Unlike totem-pole outputs, it avoids contention during mixed-mode use, and the PCA9674D,518 leverages this for direct LED drive without external components.

Does the PCA9674D,518 support hardware reset, and what is the role of the INT pin?

The PCA9674D,518 does not include a dedicated hardware reset pin but supports Software Reset via the I²C General Call address (00h) followed by data byte 06h. The INT pin is an active-low open-drain interrupt output that asserts when any input port state changes relative to its register value. This allows the host MCU to respond asynchronously to button presses or sensor events without continuous polling-reducing CPU load and power consumption. The PCA9674D,518 requires an external pull-up resistor on INT for proper operation.

What are the valid supply voltage and temperature ranges for the PCA9674D,518?

The PCA9674D,518 operates over a supply voltage range of 2.3 V to 5.5 V and is specified for ambient temperatures from −40 °C to +85 °C. Its I/O pins are 5.5 V tolerant when referenced to VDD, allowing safe interfacing with higher-voltage peripherals. The device draws only 4.5 µA typical standby current, making it ideal for battery-powered applications. These specifications are fully validated per NXP's PCA9674_PCA9674A Rev. 7 datasheet, ensuring the PCA9674D,518 meets industrial-grade reliability requirements.

Can multiple PCA9674D,518 devices share the same I²C bus, and how are addresses assigned?

Yes, up to 64 PCA9674D,518 devices can coexist on a single I²C bus using three hardware address pins (AD0, AD1, AD2). These pins accept VDD, VSS, SDA, or SCL references to generate 64 unique 7-bit slave addresses (e.g., 20h–7Fh and A0h–FFh). Address decoding is performed internally without pull-up/pull-down resistors on ADx pins-external connections must be made to define the address. The PCA9674D,518's non-overlapping address space with PCA9674A enables up to 126 total expanders on one bus, supporting complex I/O consolidation in servers and PLCs.