NXP Semiconductors PCA9544APW/G-T

Overview

PCA9544APW/G-T 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 buses. It is used in server management systems to isolate and route I²C traffic among multiple sensor banks while consolidating interrupt signals.

For engineers reviewing the PCA9544APW/G-T datasheet, PCA9544APW/G-T pinout, PCA9544APW/G-T application, or PCA9544APW/G-T equivalent, key selection criteria include its 20-pin TSSOP package, 4-channel interrupt aggregation, low Ron (≤11 Ω), 5 V-tolerant I/O, and support for hot insertion without bus glitches.

Technical Context

The PCA9544APW/G-T implements a programmable channel-select control register (B2–B0) that enables only one of four downstream SCx/SDx I²C channels at a time, with automatic HIGH-state initialization after STOP condition to prevent false bus transitions. Its pass-gate architecture uses VDD as a voltage clamp reference to enable bidirectional level translation across mismatched bus voltages.

Interrupt handling is implemented via four active-low inputs (INT0–INT3), each tied to a downstream channel, feeding an open-drain AND-combined output (INT). The control register's upper four bits (INT3–INT0) are read-only status flags indicating pending interrupts per channel, allowing master software to identify and service interrupt sources without prior channel selection.

Key Specifications

Pinout & Package

TSSOP20 package: 20-lead plastic thin shrink small outline package, body width 4.4 mm, lead pitch 0.65 mm, exposed pad not present (unlike HVQFN20), suitable for automated surface-mount assembly with standard reflow profiles.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9544APWR and PCA9545APW, the PCA9544APW/G-T offers optimal cost-performance balance for commercial-grade server and telecom applications within −40 °C to +85 °C, with proven interoperability in multi-vendor I²C ecosystems and full NXP technical support coverage.

Availability

PCA9544APW/G-T is available at Aetrix Electronics and suitable for server baseboard management, industrial sensor hubs, telecom line card monitoring, and automotive ADAS domain controllers requiring stable component supply and long-term lifecycle assurance.

Supply support for PCA9544APW/G-T 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 communication infrastructure markets.

The PCA9544A product line delivers scalable I²C bus expansion and voltage translation for resource-constrained embedded controllers, targeting applications where bus isolation, interrupt consolidation, and mixed-voltage interoperability are critical design requirements.

FAQ

What is the primary function of the PCA9544APW/G-T in an I²C system?

The PCA9544APW/G-T functions as a 1-of-4 bidirectional I²C-bus multiplexer that routes upstream SCL/SDA signals to one of four downstream channel pairs (SC0/SD0 through SC3/SD3), enabling bus segmentation and voltage translation. It also aggregates four independent interrupt inputs into a single open-drain INT output. This allows a host controller to manage multiple I²C peripherals without address conflicts while minimizing GPIO usage. The PCA9544APW/G-T is essential in systems like server BMCs where space, power, and signal integrity constraints demand efficient bus resource sharing.

Does the PCA9544APW/G-T require external level-shifting circuitry when connecting 3.3 V and 5 V I²C devices?

No, the PCA9544APW/G-T does not require external level shifters. Its pass-gate architecture uses the VDD supply voltage to clamp the maximum voltage passed between upstream and downstream buses. When VDD is set to 3.3 V, it safely translates signals between a 5 V upstream bus and 3.3 V downstream peripherals. External pull-up resistors on each SCx/SDx pair must match their respective bus voltage. All I/O pins are 5 V tolerant, ensuring robust interfacing across mixed-voltage domains without added components. This capability is intrinsic to the PCA9544APW/G-T design and verified across its full operating range.

How does the interrupt logic of the PCA9544APW/G-T operate, and how can a host processor identify which channel triggered an interrupt?

The PCA9544APW/G-T features four active-low interrupt inputs (INT0–INT3), one per downstream channel, and a single open-drain interrupt output (INT) that asserts LOW when any input is active. To identify the source, the host reads the control register: bits 7–4 (INT3–INT0) reflect the real-time status of each interrupt input. For example, reading 0b1000 indicates INT3 is active. The host then writes the corresponding channel select bits (B2–B0) to enable that channel and communicate directly with the triggering device. This mechanism is fully supported in the PCA9544APW/G-T and requires no additional hardware.

What package type and dimensions does the PCA9544APW/G-T use, and is it compatible with standard SMT assembly processes?

The PCA9544APW/G-T uses the TSSOP20 package (SOT360-1): 20-lead plastic thin shrink small outline package with 4.4 mm body width, 0.65 mm lead pitch, and 1.1 mm maximum height. It is fully compatible with standard reflow soldering processes per J-STD-020, including peak temperatures up to 260 °C. Unlike the HVQFN20 variant, it has no exposed thermal pad, simplifying stencil design and inspection. The PCA9544APW/G-T's TSSOP20 footprint is widely supported in automated placement and AOI systems, making it suitable for high-volume manufacturing without process modification.

Can the PCA9544APW/G-T be used in hot-swap or live-insertion scenarios without disrupting the upstream I²C bus?

Yes, the PCA9544APW/G-T supports hot insertion. Its power-on reset (POR) circuit holds all channels deselected and disables pass gates until VDD stabilizes above VPOR (1.5–2.1 V), preventing bus contention or false START/STOP conditions. The device exhibits no glitch on power-up and maintains high-impedance states on all SCx/SDx lines during power ramp. This behavior is inherent to the PCA9544APW/G-T silicon design and validated across its full temperature range. As a result, modules containing the PCA9544APW/G-T can be safely inserted or removed while the host I²C bus remains operational-a key requirement in FRU-based server and telecom architectures.