NXP Semiconductors PCA9557D/DG,118

Overview

PCA9557D/DG,118 from NXP Semiconductors is an 8-bit I²C-bus and SMBus I/O port expander with active LOW reset input, open-drain IO0, and programmable input/output configuration. It operates from 2.3 V to 5.5 V, supports up to 400 kHz clock frequency, and features polarity inversion, noise-filtered SCL/SDA inputs, and power-on reset - enabling reliable peripheral expansion in space-constrained industrial control and sensor interface applications.

For engineers reviewing the PCA9557D/DG,118 datasheet, PCA9557D/DG,118 pinout, PCA9557D/DG,118 application, or PCA9557D/DG,118 equivalent, this device serves as a low-standby-current (≤1 µA), 5 V-tolerant I/O expander for embedded systems requiring flexible GPIO management via standard I²C protocol without external pull-ups on address pins.

Technical Context

The PCA9557D/DG,118 implements an I²C slave interface with fixed 7-bit address (0x1C–0x1F) determined by A2–A0 pins, supporting Standard- and Fast-mode (up to 400 kHz). Its internal register map includes Input Port (read-only), Output Port (read/write), Polarity Inversion (read/write), and Configuration (read/write) registers - allowing per-pin direction and polarity control independent of data state.

Each of the eight I/Os (IO0–IO7) is individually configurable: IO0 is high-impedance open-drain with ≤1 µA leakage at VOH = 4.6 V; IO1–IO7 support push-pull outputs with ±50 mA absolute max current per pin and 20 mA per bit sourcing limit. The RESET pin triggers full register initialization without power cycle, and internal POR activates at VPOR = 1.65–2.1 V.

Key Specifications

Pinout & Package

PCA9557D/DG,118 uses the SO16 (SOT109-1) package: plastic small outline, 16 leads, 3.9 mm body width, with gull-wing leads and standard surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9555D,118 and TCA9534APWR, the PCA9557D/DG,118 uniquely combines hardware reset, open-drain IO0, and ultra-low standby current in SO16 - making it optimal for fault-resilient industrial I/O expansion where deterministic recovery and mixed-voltage compatibility are required.

Availability

PCA9557D/DG,118 is available at Aetrix Electronics and suitable for industrial control panels, sensor interface modules, and embedded reset management systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for PCA9557D/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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with leadership in I²C ecosystem components and robust qualification standards.

The PCA9557 product line delivers cost-effective, pin-compatible I/O expansion for resource-constrained embedded systems - designed specifically to simplify GPIO scaling in industrial HMIs, sensor nodes, and modular control units.

FAQ

What is the function of the RESET pin on the PCA9557D/DG,118?

The RESET pin on the PCA9557D/DG,118 is an active LOW asynchronous input that forces all internal registers (Input Port, Output Port, Polarity Inversion, Configuration) and the I²C-bus state machine into their default power-on states without requiring a power cycle. This enables rapid recovery from I²C bus hangs or configuration errors, and the pin must be pulled HIGH via external resistor when not actively driven.

Can the PCA9557D/DG,118 operate with a 3.3 V microcontroller while driving 5 V LEDs?

Yes. The PCA9557D/DG,118 supports 2.3 V to 5.5 V VDD operation and has 5 V tolerant I/O pins. When powered from 3.3 V, its IO1–IO7 outputs can safely sink current from 5 V LED anodes (with appropriate series resistors), and IO0's open-drain structure allows direct connection to 5 V pull-up networks - enabling mixed-voltage peripheral control without level shifters.

How does the polarity inversion register affect input readings on the PCA9557D/DG,118?

The polarity inversion register (Register 2) flips the logical sense of input pins defined as inputs in the Configuration register. If bit N0 = 1, then the value read from I0 in the Input Port register is inverted relative to the physical pin voltage. This allows firmware to treat active-low sensors as active-high in software - eliminating conditional logic for signal inversion and simplifying driver development.

What is the maximum number of PCA9557D/DG,118 devices supported on a single I²C bus?

Up to eight PCA9557D/DG,118 devices can share one I²C bus using the A0, A1, and A2 address pins, which configure the three LSBs of the 7-bit slave address (fixed prefix 0b0011xxx). All address pins must be externally biased - no internal pull-ups - and each combination yields a unique address from 0x1C to 0x1F, enabling scalable multi-node I/O expansion.

Does the PCA9557D/DG,118 require external pull-up resistors on SCL and SDA lines?

Yes. The PCA9557D/DG,118 has open-drain SDA and push-pull SCL drivers, but neither includes internal pull-up resistors. External pull-ups to VDD are mandatory on both SCL and SDA to ensure proper I²C bus operation, with values selected based on bus capacitance and desired rise time - typically 2.2 kΩ to 10 kΩ for standard-mode (100 kHz) and 1 kΩ to 4.7 kΩ for fast-mode (400 kHz) operation.