NXP Semiconductors PCA9671D,112

Overview

PCA9671D,112 from NXP Semiconductors is a 16-bit quasi-bidirectional I/O expander for Fast-mode Plus (Fm+) I²C-bus systems, featuring 1 MHz bus speed, 25 mA per-pin sink capability, and active-low RESET input. It replaces PCF8575 with higher drive strength (30 mA SDA), 400 mA total package sink, and 64 programmable slave addresses - enabling LED dimming control in signage and industrial I/O expansion.

For engineers reviewing the PCA9671D,112 datasheet, PCA9671D,112 pinout, PCA9671D,112 application, or PCA9671D,112 equivalent, key selection criteria include I²C-bus timing compliance at 1 MHz, 2.3–5.5 V operation with 5.5 V-tolerant I/Os, latched output behavior, and RESET-driven initialization - critical for reliable remote GPIO in space-constrained embedded systems.

Technical Context

The PCA9671D,112 implements a quasi-bidirectional I/O architecture where all 16 pins (P00–P07, P10–P17) default to HIGH at power-up and function as inputs without direction control. Its internal Power-On Reset (POR) and hardware RESET pin initialize registers to known states, eliminating reliance on software-only reset sequences.

I²C-bus communication uses standard 7-bit addressing with three address pins (AD0–AD2) supporting 64 unique slave addresses; reserved addresses (e.g., General Call 00h, Device ID F4h) enable system-level software reset and manufacturer/device identification reads - distinct from PCF8575's interrupt-based signaling.

Key Specifications

Pinout & Package

PCA9671D,112 is packaged in SO24 (SOT137-1), a plastic small outline package with 24 leads and 7.5 mm body width. Pin functions are electrically identical across SO24, TSSOP24, HVQFN24, and DHVQFN24 variants.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCF8575T, PCA9671D,112 delivers 2.5× faster bus speed and 4× higher sink capacity - enabling LED dimming and denser I/O nodes. Versus PCA9673D,112, it trades interrupt capability for deterministic hardware reset, simplifying fault recovery in industrial controllers.

Availability

PCA9671D,112 is available at Aetrix Electronics and suitable for LED signage, industrial PLCs, and medical panel interfaces requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9671D,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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9671D,112 belongs to NXP's Fast-mode Plus I²C I/O expander family, designed specifically to replace legacy PCF857x devices with enhanced speed, drive strength, and system-level reset functionality for modern embedded control systems.

FAQ

What is the maximum I²C-bus clock frequency supported by PCA9671D,112?

The PCA9671D,112 supports up to 1 MHz I²C-bus operation as a Fast-mode Plus (Fm+) device. This is confirmed in the datasheet's Features section and electrical characteristics, enabling faster data transfer than standard Fast-mode (400 kHz) expanders like the PCF8575. The 1 MHz capability is essential for time-sensitive applications such as LED PWM dimming and real-time I/O updates in the PCA9671D,112.

Does PCA9671D,112 have built-in pull-up resistors on its address pins AD0–AD2?

No, the PCA9671D,112 does not include internal pull-up resistors on AD0, AD1, or AD2. As stated in Section 7.1, "To conserve power, no internal pull-up resistors are incorporated on AD2, AD1, and AD0." External biasing is required to set valid logic levels for slave address configuration. This design choice minimizes quiescent current and ensures predictable address selection in the PCA9671D,112.

How does the RESET pin function on PCA9671D,112 compared to the PCF8575?

The PCA9671D,112 replaces the PCF8575's interrupt (INT) output with an active-low RESET input. Holding RESET LOW for ≥tw(rst) forces all I/Os and registers into their power-up default state - a hardware-initiated reset independent of I²C-bus activity. This differs fundamentally from PCF8575's INT signal, which only reports input changes. The RESET feature enhances system reliability in the PCA9671D,112.

Can PCA9671D,112 drive LEDs directly without external transistors?

Yes, the PCA9671D,112 can drive standard LEDs directly: each of its 16 I/O pins provides 25 mA sink current, and the total package sink capacity is 400 mA. This is explicitly stated in the General Description and Features sections. When used within these limits - e.g., 16 LEDs at 25 mA each - no external drivers are needed, simplifying designs using the PCA9671D,112 for indicator or display applications.

What is the purpose of the Device ID read function in PCA9671D,112?

The Device ID read function in PCA9671D,112 provides a 24-bit read-only identifier containing manufacturer code (8 bits), part identification (13 bits), and die revision (3 bits). Accessed via reserved I²C address F4h, it enables firmware validation, field diagnostics, and automated BOM verification. This feature is documented in Section 7.2.2 and distinguishes the PCA9671D,112 from basic expanders lacking traceability features.