NXP Semiconductors PCA9555HF,118

Overview

PCA9555HF,118 from NXP Semiconductors is a 16-bit I²C-bus/SMBus GPIO expander in HWQFN24 package, providing two 8-bit configurable I/O ports with individual direction control, polarity inversion, and open-drain interrupt output. It operates from 2.3 V to 5.5 V, tolerates 5 V on I/O pins, supports up to 400 kHz I²C clock, and targets embedded system expansion for sensors, push buttons, LEDs, and fan control.

For engineers reviewing the PCA9555HF,118 datasheet, PCA9555HF,118 pinout, PCA9555HF,118 application, or PCA9555HF,118 equivalent, this page delivers verified pin functions, real-world use cases, validated alternatives, thermal pad layout guidance, and I²C timing constraints critical for reliable integration into space-constrained industrial and consumer designs.

Technical Context

The PCA9555HF,118 implements dual 8-bit port architecture with independent configuration, input, output, and polarity inversion registers-each accessible via I²C command byte addressing. Its interrupt logic activates only on state change of input-configured pins and clears upon reading the corresponding input port register.

It features noise filtering on SCL/SDA inputs, internal power-on reset (VPOR = 1.5–1.65 V), and hardware address selection via A0–A2 pins enabling up to eight devices on one bus. All I/Os default to high-impedance inputs with weak pull-ups to VDD at power-up.

Key Specifications

Pinout & Package

PCA9555HF,118 uses HWQFN24 (SOT994-1) package: 4 mm × 4 mm × 0.75 mm body, no leads, 24-terminal thermal-enhanced quad flat. Exposed center pad must be soldered to PCB thermal pad with vias for optimal thermal performance and electrical stability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9555PW,118 and PCA9555BS,118, the PCA9555HF,118 offers the lowest profile (0.75 mm) and best thermal performance among PCA9555 variants, making it optimal for space-constrained, high-density, or thermally sensitive applications where minimal Z-height and efficient heat dissipation are critical.

Availability

PCA9555HF,118 is available at Aetrix Electronics and suitable for industrial sensor hubs, consumer keypad interfaces, LED status array controllers, and fan speed monitor & control systems requiring stable component supply and long-term manufacturability.

Supply support for PCA9555HF,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 leader focused on secure connectivity solutions for automotive, industrial, IoT, mobile, and communication infrastructure markets.

The PCA9555 product line delivers scalable, low-power I²C GPIO expansion for resource-constrained embedded systems - designed specifically to simplify peripheral interfacing while maintaining robustness, interoperability, and ease of firmware integration.

FAQ

What is the I²C address range supported by the PCA9555HF,118?

The PCA9555HF,118 supports seven fixed I²C slave addresses (0x20–0x27) determined by the logic states of A0, A1, and A2 pins. All addresses follow the standard 7-bit format with R/W bit appended during transmission. No software address configuration is required - addressing is purely hardware-based and fully compatible with standard I²C masters. This enables up to eight PCA9555HF,118 devices on a single bus without address conflicts.

Does the PCA9555HF,118 require external pull-up resistors on SCL and SDA lines?

Yes, the PCA9555HF,118 requires external pull-up resistors on both SCL and SDA lines, as specified in the I²C-bus standard. The device does not integrate internal pull-ups. Typical values range from 1.8 kΩ to 10 kΩ depending on bus capacitance and speed (standard or fast mode). Proper sizing ensures reliable rise times and noise immunity - undersized resistors increase power consumption; oversized ones risk timing violations. This requirement applies identically across all PCA9555HF,118 implementations.

How does the interrupt output (INT) of the PCA9555HF,118 behave during power-up?

The INT pin of the PCA9555HF,118 is actively driven LOW during power-on reset and remains LOW until the internal power-on reset completes and the device enters normal operation. After reset release, INT floats HIGH (open-drain) and only asserts LOW when an input state change occurs on a pin configured as input. No external de-bounce or latching circuitry is needed - the PCA9555HF,118 handles edge detection and assertion internally, and reading the relevant input port register clears the interrupt condition.

Can the PCA9555HF,118 drive LEDs directly without external current-limiting components?

The PCA9555HF,118 can sink up to 20 mA per I/O pin (with total device limit of 160 mA sourced or 200 mA sunk), making it capable of driving standard LEDs directly when configured as open-drain outputs with appropriate external pull-up to VDD. However, a series current-limiting resistor is still required to set LED current and prevent exceeding absolute maximum ratings. The PCA9555HF,118 does not integrate current regulation - resistor value must be calculated based on VDD, LED forward voltage, and desired current.

Is the exposed thermal pad on the PCA9555HF,118 electrically connected, and how must it be handled in PCB layout?

Yes, the exposed center pad on the PCA9555HF,118 (HWQFN24) is electrically connected to VSS and must be soldered to a PCB thermal pad tied to the system ground plane. It is not optional - failure to connect compromises thermal performance, electrical stability, and ESD robustness. Layout requires thermal vias (≥4× 0.3 mm diameter) under the pad, connected to inner-layer ground planes, and a minimum 4 mm × 4 mm copper area. This ensures reliable operation at full rated current and ambient temperatures up to +85 °C.