NXP Semiconductors PCA9544AD,112

Overview

PCA9544AD,112 from NXP Semiconductors is a 1-of-4 bidirectional I²C-bus translating multiplexer with integrated interrupt logic, operating from 2.3 V to 5.5 V supply, supporting up to 400 kHz clock frequency, and enabling voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V I²C buses in server management and multi-voltage sensor subsystems.

For engineers reviewing the PCA9544AD,112 datasheet, PCA9544AD,112 pinout, PCA9544AD,112 application, or PCA9544AD,112 equivalent, this device delivers channel-selectable bus isolation, active-low interrupt aggregation, and 5 V-tolerant I/O-critical for fault-tolerant I²C expansion in industrial control, telecom chassis, and embedded baseboard management controllers (BMCs).

Technical Context

The PCA9544AD implements a programmable 4-channel switch matrix controlled via I²C write to an 8-bit register where bits B2–B0 select one downstream SCx/SDx pair while INT3–INT0 status bits (read-only) reflect pending interrupts per channel. Its pass-gate architecture uses VDD as a voltage clamp reference, enabling bidirectional level translation without external translators.

Interrupt handling operates independently of channel selection: any active LOW signal on INT0–INT3 drives the open-drain INT output LOW and sets corresponding bits in the control register, allowing the master to poll and route to the interrupting channel without prior channel enablement.

Key Specifications

Pinout & Package

PCA9544AD,112 is housed in a plastic small outline package (SO20), 20-pin, 7.5 mm body width (SOT163-1), with gull-wing leads and standard marking. Thermal resistance R_th(j-a) is 90 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar I²C-bus multiplexer applications.

Compared with TCA9544A and PCA9548AD, the PCA9544AD,112 offers optimal balance of speed (400 kHz), thermal performance (SO20 R_th(j-a) = 90 °C/W), and pin compatibility for established 4-channel designs-making it ideal for space-constrained, high-reliability deployments where upgrade path to 8 channels is not immediate.

Availability

PCA9544AD,112 is available at Aetrix Electronics and suitable for server BMCs, industrial sensor hubs, telecom line cards, and automotive diagnostic modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for PCA9544AD,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 deep expertise in I²C, SMBus, and power management ICs.

The PCA9544A product line was designed specifically to solve I²C bus contention and voltage domain bridging challenges in dense, multi-peripheral embedded systems-targeting baseboard management, modular computing, and intelligent sensor networks.

FAQ

What is the maximum I²C clock frequency supported by the PCA9544AD,112?

The PCA9544AD,112 supports I²C clock frequencies up to 400 kHz, meeting Fast-mode I²C specifications. This allows full compatibility with high-speed peripherals such as fast EEPROMs and real-time sensor arrays without timing constraint violations or added protocol overhead.

How does the PCA9544AD,112 handle voltage translation between different I²C bus rails?

The PCA9544AD,112 uses its VDD supply voltage as a reference to clamp the high-level output voltage (Vo(sw)) on downstream SCx/SDx lines. When VDD is set to 3.3 V, Vo(sw) is limited to ~2.8 V, enabling safe communication with 1.8 V or 2.5 V devices while remaining compatible with 5 V upstream hosts.

Can the PCA9544AD,112 be used without connecting all four downstream channels?

Yes-the PCA9544AD,112 supports partial channel usage. Unused SCx/SDx pairs can remain unconnected, and unused INT0–INT3 inputs must be pulled HIGH to VDD. The control register defaults to "no channel selected" on power-up, ensuring safe initialization regardless of downstream configuration.

What is the function of the INT output, and how is it driven?

The INT output of the PCA9544AD,112 is an open-drain active LOW signal that functions as a logical AND of INT0–INT3. It is driven LOW whenever any downstream interrupt input is asserted, and returns HIGH only when all four INTn inputs are deasserted-enabling efficient interrupt coalescing for host firmware.

Does the PCA9544AD,112 require external pull-up resistors on its I²C lines?

Yes-external pull-up resistors are required on all I²C lines: upstream SCL/SDA and each downstream SCx/SDx pair. Pull-up values depend on bus capacitance and speed; typical values range from 1 kΩ (fast-mode, low-capacitance) to 10 kΩ (standard-mode, high-capacitance), as specified in I²C-bus standards.