NXP Semiconductors PCA9555PW/DG,118

Overview

PCA9555PW/DG,118 from NXP Semiconductors is a 16-bit I²C-bus/SMBus GPIO expander in TSSOP24 package, providing configurable parallel I/O for embedded control systems. It operates from 2.3 V to 5.5 V, supports 5 V-tolerant I/Os, delivers up to 20 mA per pin, and features an active-low open-drain interrupt output. It is used in industrial HMI panels to extend microcontroller I/O for keypad scanning and LED status indication.

For engineers reviewing the PCA9555PW/DG,118 datasheet, PCA9555PW/DG,118 pinout, PCA9555PW/DG,118 application, or PCA9555PW/DG,118 equivalent, key selection criteria include I²C address configurability (A0–A2), polarity inversion register support, input state change interrupt behavior, and 5 V I/O tolerance in mixed-voltage systems.

Technical Context

The PCA9555PW/DG,118 implements two independent 8-bit I/O ports (Port 0 and Port 1), each with dedicated configuration, input, output, and polarity inversion registers. Its I²C interface supports standard (100 kHz) and fast-mode (400 kHz) clock rates, and includes noise filtering on SCL/SDA inputs to improve bus robustness in noisy environments.

Interrupt generation is triggered only when an input pin's logic level differs from its corresponding Input Port register value - not by output changes - and is cleared upon reading the relevant port register. Power-on reset initializes all registers to default states, including 16 high-impedance inputs with internal weak pull-ups to VDD.

Key Specifications

Pinout & Package

TSSOP24 package (SOT355-1), 4.4 mm body width, 0.65 mm pitch, 24-lead plastic thin shrink small outline package.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar GPIO expander applications.

Compared with PCA9554PW,118, the PCA9555PW/DG,118 doubles I/O capacity and adds polarity inversion - critical for heterogeneous sensor interfaces. Against TCA6424APWR, it trades 5 V tolerance and wider VDD range for lower maximum sink current and no hardware reset, making it more suitable for mixed-voltage industrial retrofits.

Availability

PCA9555PW/DG,118 is available at Aetrix Electronics and suitable for industrial HMIs, PLC I/O expansion, and sensor aggregation systems requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9555PW/DG,118 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 PCA9555 product line was designed to extend microcontroller I/O in resource-constrained embedded systems using standardized I²C infrastructure - targeting industrial control, building automation, and appliance interfaces where reliability and voltage flexibility are critical.

FAQ

What is the I²C slave address range supported by the PCA9555PW/DG,118?

The PCA9555PW/DG,118 supports seven user-configurable I²C slave addresses (0x20–0x26) via A0–A2 pins, plus one fixed address (0x27) when all address pins are high. This allows up to eight PCA9555PW/DG,118 devices on a single I²C bus without address conflict. The base address is 0x20, and each combination of A0/A1/A2 increments the address by 1.

Does the PCA9555PW/DG,118 require external pull-up resistors on SDA and SCL lines?

Yes, the PCA9555PW/DG,118 requires external pull-up resistors on both SDA and SCL lines because its I²C interface uses open-drain outputs. Typical values range from 1.8 kΩ to 10 kΩ depending on bus capacitance and speed - 4.7 kΩ is recommended for 400 kHz operation with moderate trace length. The PCA9555PW/DG,118 itself does not integrate pull-ups.

How does the interrupt output (INT) behave when multiple input pins change simultaneously on the PCA9555PW/DG,118?

The INT pin on the PCA9555PW/DG,118 is asserted low whenever *any* configured input pin changes state relative to its Input Port register value - regardless of how many pins change. It remains asserted until the corresponding Input Port register (Port 0 or Port 1) is read, which clears the interrupt condition for that port only. Simultaneous changes across both ports will keep INT active until both ports are read.

Can the PCA9555PW/DG,118 drive LEDs directly, and what current limits apply?

Yes, the PCA9555PW/DG,118 can drive LEDs directly in sink mode (common-anode configuration). Each I/O pin supports up to 20 mA sink current at VOL ≤ 0.5 V (VDD ≥ 2.3 V), with total device sink limit of 200 mA across all pins. For reliable operation, external current-limiting resistors must be used, and per-port current (8 pins) must not exceed 100 mA. The PCA9555PW/DG,118 does not support source-mode LED drive above 8 mA.

Is the PCA9555PW/DG,118 pin-compatible with the PCA9554 series?

Yes, the PCA9555PW/DG,118 is pin-compatible with the PCA9554PW,118 in the same TSSOP24 package and shares identical pin functions and I²C address mapping. However, software is not compatible due to added registers (polarity inversion, enhanced configuration) and different default register values - firmware must be updated to initialize and access the extended feature set of the PCA9555PW/DG,118.