NXP Semiconductors PCA9555BSHP

Overview

The PCA9555BSHP from NXP Semiconductors is a 16-bit I²C-bus/SMBus GPIO expander in HVQFN24 package, providing configurable parallel input/output expansion for microcontroller systems. It features 5 V-tolerant I/Os, active-low open-drain interrupt output, polarity inversion registers, and individual I/O direction control. It is used in industrial control panels to manage push buttons, LEDs, and sensor interfaces while maintaining compatibility with existing I²C infrastructure.

For engineers reviewing the PCA9555BSHP datasheet, PCA9555BSHP pinout, PCA9555BSHP application, or PCA9555BSHP equivalent, key selection criteria include I²C address configurability (A0–A2), 2.3 V to 5.5 V supply operation, 5 V I/O tolerance, interrupt-driven input change detection, and HVQFN24 thermal performance for space-constrained embedded designs.

Technical Context

The PCA9555BSHP 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 internal noise filtering on SCL/SDA enhances bus robustness in electrically noisy environments.

Power-on reset initializes all I/Os as high-impedance inputs with weak pull-ups to VDD, and the open-drain INT output asserts when any input pin state differs from its corresponding Input Port register - cleared only by reading that specific port's Input register. Address pins A0–A2 allow up to eight devices on one I²C bus.

Key Specifications

Pinout & Package

HVQFN24 package (4 mm × 4 mm × 0.85 mm), thermally enhanced with exposed center pad soldered to PCB ground plane for improved thermal dissipation and electrical stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA6424A and PCA9539, the PCA9555BSHP uniquely delivers per-port polarity inversion, 5 V I/O tolerance at 2.3 V VDD, and deterministic power-on reset - making it optimal for industrial and medical systems requiring robust, configurable, and glitch-free I/O expansion.

Availability

The PCA9555BSHP is available at Aetrix Electronics and suitable for industrial control panels, smart HVAC thermostats, medical infusion pump UIs, and automated test equipment requiring stable component supply across long production lifecycles.

Supply support for PCA9555BSHP 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, with leadership in I²C ecosystem components.

The PCA9555BSHP belongs to NXP's I²C GPIO expander product line, designed specifically to extend microcontroller I/O capability in space- and power-constrained embedded systems while maintaining industrial-grade reliability and interoperability.

FAQ

What is the I²C address range supported by the PCA9555BSHP?

The PCA9555BSHP supports seven programmable slave addresses (0x20–0x26) via A0–A2 pins, plus one fixed address (0x27) when all address pins are high. This allows up to eight PCA9555BSHP devices on a single I²C bus without address conflict, enabling scalable I/O expansion in multi-node systems.

Does the PCA9555BSHP require external pull-up resistors on SCL and SDA lines?

Yes, the PCA9555BSHP requires external pull-up resistors on both SCL and SDA lines, as its I²C interface uses open-drain outputs. Typical values range from 2.2 kΩ to 10 kΩ depending on bus capacitance and desired rise time; NXP recommends 4.7 kΩ for standard-mode operation at 100 kHz.

How does the interrupt (INT) pin of the PCA9555BSHP behave after a state change?

The PCA9555BSHP INT pin goes low when any input pin's state differs from its corresponding Input Port register value. The interrupt remains asserted until the host reads the specific Input Port register (Port 0 or Port 1) that triggered it - reading the wrong port does not clear the INT signal.

Can the PCA9555BSHP drive LEDs directly without external transistors?

Yes, the PCA9555BSHP can drive LEDs directly in sink mode: each I/O pin supports up to 20 mA sink current (with VOL ≤ 0.5 V at VDD = 5.5 V), and total device sink current is limited to 200 mA. For higher-current or high-side LED driving, external FETs are recommended.

Is the exposed thermal pad on the HVQFN24 package of the PCA9555BSHP electrically connected?

Yes, the exposed center pad of the PCA9555BSHP HVQFN24 package is internally connected to VSS and must be soldered to a PCB thermal pad tied to ground. This connection is mandatory for proper device operation, thermal management, and electrical stability - floating the pad may cause malfunction or reduced ESD immunity.