NXP Semiconductors PCA9501D,112

Overview

The PCA9501D,112 from NXP Semiconductors is an 8-bit I²C-bus/SMBus I/O expander with integrated 2-kbit EEPROM, quasi-bidirectional GPIO pins (IO0–IO7), active LOW open-drain interrupt output (INT), and six hardware address pins (A0–A5) enabling up to 64 devices on one bus. It operates from 2.5 V to 3.6 V, supports 400 kHz clock frequency, and is rated for −40 °C to +85 °C ambient temperature - used for board version tracking, health monitoring, and hot-pluggable card interfaces in telecom backplanes.

For engineers reviewing the PCA9501D,112 datasheet, PCA9501D,112 pinout, PCA9501D,112 application, or PCA9501D,112 equivalent, key selection criteria include its dual-device I²C addressing (GPIO at 0x60–0x6F, EEPROM at 0xE0–0xE7), 5 V-tolerant I/Os, self-timed 5 ms EEPROM write cycle, and hot-insertion support in multi-card systems.

Technical Context

The PCA9501D,112 implements a unified I/O expander core with independent input/output configuration per pin via an 8-bit control register, synchronized to the I²C-bus protocol. Its interrupt logic detects any input state change versus port register value and asserts the open-drain INT line within 4 µs.

EEPROM access uses separate fixed I²C addresses (starting with '1'), decoupled from GPIO addressing (starting with '0'), allowing concurrent read/write operations without bus contention. The WC pin enables hardware write protection, and internal pull-ups on A0–A5 simplify address configuration across up to 64 nodes.

Key Specifications

Pinout & Package

PCA9501D,112 is supplied in SO20 (SOT163-1) package: plastic small outline, 20 leads, 7.5 mm body width, lead pitch 1.27 mm. Pin 1 index marked; exposed pad not present.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9555D,112, the PCA9501D,112 trades I/O count for integrated EEPROM - eliminating external memory and reducing layout complexity. Against TCA6424ARGJR, it offers identical functionality at lower cost in established NXP supply chains but lacks extended temperature rating.

Availability

PCA9501D,112 is available at Aetrix Electronics and suitable for telecom backplane monitoring, industrial HMI panel interfaces, and field-serviceable embedded systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9501D,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 company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9501D,112 belongs to NXP's I²C-bus I/O expander product line, designed specifically for board-level monitoring, configuration storage, and hot-pluggable subsystem interfacing in telecom and industrial infrastructure.

FAQ

What is the I²C-bus address scheme used by the PCA9501D,112?

The PCA9501D,112 uses two distinct I²C-bus addresses: GPIO functions respond to addresses starting with '0' (e.g., 0x60–0x6F), while the EEPROM responds to addresses starting with '1' (e.g., 0xE0–0xE7). Address bits A0–A5 are hardware-configurable, allowing up to 64 devices per bus segment. This dual-address architecture lets the PCA9501D,112 appear as two independent slaves - simplifying software access and avoiding register banking.

How does the interrupt function work on the PCA9501D,112?

The PCA9501D,112 features an active LOW open-drain INT pin that asserts when any input pin's state differs from its corresponding bit in the input port register. The interrupt is valid within 4 µs (tv(INT)) and resets automatically after reading/writing the affected port or restoring the original input state. No external debouncing is required - the PCA9501D,112 handles edge detection internally, making it ideal for low-latency status monitoring in telecom and industrial systems.

Can the PCA9501D,112 operate with a 5 V microcontroller I²C interface?

Yes - all I/O, SDA, SCL, and address pins of the PCA9501D,112 are 5 V tolerant, even when VDD is powered at 2.5–3.6 V. This allows direct connection to 5 V I²C masters without level shifters. However, pull-up resistors must be tied to the master's VCC (e.g., 5 V), and the PCA9501D,112's own VDD must remain within its specified 2.5–3.6 V range. This tolerance simplifies integration into mixed-voltage systems.

What is the EEPROM write protection mechanism on the PCA9501D,112?

The PCA9501D,112 uses a dedicated active LOW Write Control (WC) pin for hardware EEPROM write protection. When WC is held HIGH, all EEPROM write operations (byte or page) are blocked - preventing accidental overwrites during power-up, noise events, or firmware bugs. Only when WC is pulled LOW can writes occur, and each write cycle completes autonomously in ≤10 ms. This ensures robust data integrity in mission-critical applications like board identification and field diagnostics.

Is the PCA9501D,112 suitable for hot-plug applications?

Yes - the PCA9501D,112 is explicitly designed for hot insertion in backplane systems. It features no-glitch power-up behavior, internal power-on reset, and robust I/O states during supply ramp-up. Combined with its interrupt-driven architecture, the PCA9501D,112 enables reliable presence detection and status reporting for removable cards without requiring system reset or manual reinitialization - a key requirement in carrier-class telecom and modular industrial equipment.