NXP Semiconductors PCA9554ATS,112

Overview

PCA9554ATS,112 from NXP Semiconductors is an 8-bit I²C-bus/SMBus GPIO expander in SSOP20 package, providing configurable input/output pins with active-low open-drain interrupt output, 2.3–5.5 V operation, and 5 V-tolerant I/Os. It enables expansion for push buttons, LEDs, sensors, and fans in space-constrained industrial control and embedded systems.

For engineers reviewing the PCA9554ATS,112 datasheet, PCA9554ATS,112 pinout, PCA9554ATS,112 application, or PCA9554ATS,112 equivalent, this page delivers verified register-level functionality, I²C address configuration (0x20–0x27), polarity inversion capability, and real-world timing behavior including 4 µs INT assertion delay and 400 kHz Fast-mode support.

Technical Context

The PCA9554ATS,112 implements a synchronous I²C slave interface with fixed 7-bit address 0x20 (A2=A1=A0=0) and supports standard- and fast-mode clocking up to 400 kHz. Its internal register map includes Input Port (read-only), Output Port (writeable), Polarity Inversion (bit-wise inversion enable), and Configuration (per-pin I/O direction) registers - all accessible via single-byte command addressing without auto-increment.

Each of its eight bidirectional I/Os defaults to high-impedance input with weak 100 kΩ pull-up at power-on reset; I/Os configured as outputs drive low with 10 mA sink capability (VOL = 0.5 V @ VDD = 3.0 V) and tolerate up to 5.5 V on input pins regardless of supply voltage. The open-drain INT output asserts when any input pin state differs from its corresponding Input Port register value.

Key Specifications

Pinout & Package

PCA9554ATS,112 uses SSOP20 package (SOT266-1), 6.6 mm × 4.5 mm × 1.2 mm body, 0.65 mm pitch, 20-pin shrink small outline with exposed pad not present. Pin 1 is marked by index notch; pin 10 is VSS (ground), pin 5 is VDD (supply), and pin 1 is INT (interrupt output).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9554D,112, PCA9554ATS,112 offers 33 % smaller PCB area (SSOP20 vs. SO16) and dedicated n.c. pins for routing flexibility; versus TCA9554APW,112, it provides higher output drive strength critical for driving multiple parallel LEDs or logic loads.

Availability

PCA9554ATS,112 is available at Aetrix Electronics and suitable for industrial control panels, smart sensor hubs, LED lighting controllers, and fan speed management systems requiring stable component supply across extended temperature ranges (−40 °C to +85 °C).

Supply support for PCA9554ATS,112 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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with core expertise in interface, power management, and microcontroller technologies.

The PCA9554 series belongs to NXP's I²C-bus I/O expander product line, designed specifically to simplify peripheral expansion in resource-constrained embedded systems while maintaining robust noise immunity and wide supply voltage operation.

FAQ

What is the default I²C address of the PCA9554ATS,112 and how is it set?

The PCA9554ATS,112 has a fixed default I²C slave address of 0x20, determined by tying A0, A1, and A2 pins to ground. This matches the PCA9554 (not PCA9554A) family variant. Address selection is hardware-configured via these three pins, allowing up to eight PCA9554ATS,112 devices on one bus - but only if their A0–A2 combinations differ. The PCA9554ATS,112 itself uses A2=A1=A0=0.

Does the PCA9554ATS,112 support hot insertion or live I²C bus connection?

The PCA9554ATS,112 does not include explicit hot-swap protection circuitry. While its 5 V-tolerant I/Os and noise-filtered SCL/SDA inputs improve robustness, connecting the device to a live I²C bus may cause bus contention or transient glitches. NXP recommends powering the PCA9554ATS,112 before enabling the I²C bus or using series resistors on SCL/SDA for marginal cases. Always verify bus arbitration behavior in your specific system.

How does the INT pin of the PCA9554ATS,112 behave during power-on reset?

During power-on reset, the INT pin of the PCA9554ATS,112 remains deasserted (high) until the internal POR circuit completes and registers initialize. Once initialized, INT asserts only when an input pin's physical state differs from its latched value in the Input Port register. No spurious interrupts occur at power-up because all I/Os default to inputs with weak pull-ups, and the Input Port reflects actual pin states after stabilization.

Can the PCA9554ATS,112 drive LEDs directly without external current-limiting resistors?

No - the PCA9554ATS,112 requires external current-limiting resistors for LED driving. Although its I/Os sink up to 10 mA per pin (VOL = 0.5 V @ VDD = 3.0 V), forward voltage and desired LED brightness dictate resistor value. For example, driving a 2 V red LED from 3.3 V requires ~130 Ω to limit current to 10 mA. Omitting the resistor risks exceeding absolute maximum ratings and damaging the PCA9554ATS,112 output stage.

What is the purpose of the n.c. (no-connect) pins on the PCA9554ATS,112 SSOP20 package?

The PCA9554ATS,112 SSOP20 package includes four n.c. pins (Pins 3, 8, 13, 18) that are electrically unconnected and serve solely for mechanical symmetry and PCB routing flexibility. They must remain unconnected in the schematic and layout - no traces, vias, or copper pours should attach to them. These pins allow cleaner signal routing around the IC and help balance thermal distribution during reflow, but provide no functional benefit.