Texas Instruments PCA9555DWR

Overview

PCA9555DWR from Texas Instruments is a 16-bit I²C/SMBus I/O expander with interrupt output, configuration registers, and 5-V-tolerant I/O ports. It operates from 2.3 V to 5.5 V, supports 400-kHz Fast Mode I²C, and provides latched push-pull outputs capable of directly driving LEDs in industrial control and server management applications.

For engineers reviewing the PCA9555DWR datasheet, PCA9555DWR pinout, PCA9555DWR application, or PCA9555DWR equivalent, this device delivers remote GPIO expansion where microcontroller pins are constrained-especially in telecom switching equipment, embedded servers, and PC peripheral interfaces requiring low-standby-current (≤1 µA) and hardware-addressable multi-device bus topology.

Technical Context

The PCA9555DWR implements two independent 8-bit I/O banks (P07–P00 and P17–P10), each with configurable input/output direction, polarity inversion, and latch control via dedicated Configuration, Input Port, Output Port, and Polarity Inversion registers. All registers are accessible over I²C with no external components required for basic operation.

Its open-drain active-low INT output asserts when any input state differs from its corresponding Input Port register value, enabling edge-triggered asynchronous notification to the host controller. Power-on reset initializes all registers to default states, and three hardware address pins (A0–A2) support up to eight devices on a shared I²C bus without software reconfiguration.

Key Specifications

Pinout & Package

PCA9555DWR is packaged in a 24-pin SOIC (DW) package measuring 15.4 mm × 7.50 mm, with standard gull-wing leads and 1.27 mm pitch. The package supports automated assembly and offers thermal performance suitable for industrial ambient temperatures (–40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9554ADWR and PCA9535CDWR, the PCA9555DWR uniquely combines full 16-bit I/O, integrated input pullups, and identical SOIC-DW footprint-making it optimal for new designs requiring maximum GPIO density with minimal external components and interrupt-aware remote control.

Availability

PCA9555DWR is available at Aetrix Electronics and suitable for server management, industrial PLC I/O expansion, and telecom router control requiring stable component supply across extended production lifecycles.

Supply support for PCA9555DWR 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies with over 50 years of innovation in industrial and communications infrastructure.

The PCA9555DWR belongs to TI's I²C I/O expander product line, designed specifically to extend microcontroller GPIO resources in space-constrained, power-sensitive, and noise-immune industrial and networking systems.

FAQ

What is the I²C address range supported by PCA9555DWR?

The PCA9555DWR supports eight fixed I²C slave addresses (0x20–0x27) determined by the logic states of hardware pins A0, A1, and A2. Each combination selects a unique 7-bit address, allowing up to eight PCA9555DWR devices to coexist on the same I²C bus without address conflict. This eliminates software address remapping and simplifies multi-device system design.

Does PCA9555DWR require external pull-up resistors on SDA and SCL lines?

Yes, PCA9555DWR requires external pull-up resistors on both SDA and SCL lines to ensure proper I²C bus operation. The datasheet specifies typical values of 4.7 kΩ for 3.3 V systems and 10 kΩ for 5 V systems. These resistors establish valid high logic levels and meet rise-time requirements for 400-kHz Fast Mode operation.

Can PCA9555DWR drive LEDs directly without external current-limiting components?

PCA9555DWR can drive LEDs directly when configured as outputs, with each I/O pin supporting up to 25 mA sink current and each octal bank limited to 100 mA total. However, an external series current-limiting resistor is still required to set the desired LED current and prevent damage - the device does not integrate current regulation.

How does the interrupt (INT) output of PCA9555DWR behave during I²C read operations?

The PCA9555DWR INT output deasserts automatically after the host reads the corresponding Input Port register - specifically at the ACK or NACK bit following the rising edge of SCL. This hardware-based reset avoids race conditions and ensures interrupt acknowledgment is tightly coupled to data retrieval, eliminating need for explicit register writes to clear INT.

Is PCA9555DWR compatible with 3.3 V microcontrollers when interfacing to 5 V peripherals?

Yes, PCA9555DWR supports 5-V-tolerant I/O pins, meaning its P00–P17 can safely accept input voltages up to 5.5 V even when VCC = 3.3 V. This allows direct connection to 5 V sensors, switches, or logic outputs without level-shifting circuitry - a key advantage in mixed-voltage industrial and telecom systems.