Texas Instruments PCA9544APWE4

Overview

PCA9544APWE4 from Texas Instruments is a low-voltage, 4-channel bidirectional I²C/SMBus multiplexer with integrated interrupt logic and voltage-level translation capability. It enables one master to selectively route SCL/SDA signals to one of four downstream I²C buses, supports 1.8-V to 5-V bus translation, operates from 2.3 V to 5.5 V, features active-low interrupt aggregation (INT0–INT3 → INT), and powers up with all channels deselected - used in server backplanes and telecom switching equipment to resolve slave address conflicts.

For engineers reviewing the PCA9544APWE4 datasheet, PCA9544APWE4 pinout, PCA9544APWE4 application, or PCA9544APWE4 equivalent, this device is selected when managing multiple identical I²C peripherals (e.g., temperature sensors), isolating faulted buses, enabling mixed-voltage I²C communication, or implementing interrupt-driven peripheral monitoring without software polling overhead.

Technical Context

The PCA9544APWE4 implements a single-control-register architecture where three LSBs select exactly one of four downstream SCn/SDn channel pairs, while four MSBs reflect real-time interrupt status from each channel. Its pass-gate switches use VCC as a voltage clamp, enabling true bidirectional level translation between 1.8-V, 2.5-V, 3.3-V, and 5-V domains without external level shifters.

Interrupt logic performs wired-AND aggregation: INT asserts low if any of INT0–INT3 is low, with 4-μs valid propagation and 2-μs reset delay. Power-on reset initializes the control register to 0x00 (all channels off) when VCC crosses VPORR (1.5 V typ.) rising and VPORF (1.0 V typ.) falling, ensuring deterministic startup behavior even after brownout.

Key Specifications

Pinout & Package

TSSOP-20 (PW) package: 6.50 mm × 4.40 mm body, 0.65 mm pitch, exposed thermal pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9544APWR, PCA9544APWE4 uses a legacy surface finish optimized for high-reliability solder joints in aerospace or medical applications; compared with PCA9548APW, it delivers identical per-channel performance at lower static power and reduced PCB area - making it optimal for space-constrained 4-peripheral systems.

Availability

PCA9544APWE4 is available at Aetrix Electronics and suitable for server backplane management, telecom router control planes, and factory automation I/O hubs requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9544APWE4 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity solutions, with decades of expertise in interface ICs and industrial-grade reliability.

The PCA9544A product line was designed specifically to solve I²C bus scalability and voltage-domain interoperability challenges in dense, multi-peripheral systems - targeting servers, networking infrastructure, and programmable logic controllers.

FAQ

What is the primary function of the PCA9544APWE4 in an I²C system?

The PCA9544APWE4 functions as a 4-channel bidirectional I²C multiplexer that enables a single master to communicate with up to four isolated downstream I²C buses. It resolves slave address conflicts by time-multiplexing access, supports voltage-level translation between 1.8-V, 2.5-V, 3.3-V, and 5-V domains, and aggregates interrupt signals from each channel into a single active-low output. The PCA9544APWE4 is essential in systems like server backplanes where multiple identical sensors share the same I²C address.

Does the PCA9544APWE4 support hot insertion of downstream I²C devices?

Yes, the PCA9544APWE4 supports hot insertion of downstream I²C devices. Its internal architecture prevents bus lockup during live connection or disconnection of slave peripherals, and its power-on reset ensures deterministic channel deselection at startup. This capability is critical in telecom router line cards and modular server architectures where field-replaceable units must be serviced without powering down the entire system. The PCA9544APWE4 maintains bus integrity even when downstream devices are added or removed mid-operation.

How does the PCA9544APWE4 handle voltage-level translation between different I²C buses?

The PCA9544APWE4 achieves voltage-level translation using VCC-referenced pass-gate switches: the VCC pin sets the maximum voltage passed through the switch, allowing 1.8-V, 2.5-V, or 3.3-V slaves to communicate with a 5-V master without external level shifters. Each downstream channel (SDn/SCn) requires its own pull-up resistor tied to its local bus voltage (VDPUx), while the upstream SDA/SCL lines pull up to the master's voltage (VDPUM). The PCA9544APWE4's 5-V tolerant inputs ensure compatibility across all supported voltage combinations.

What happens to the PCA9544APWE4 channels during power-up?

During power-up, the PCA9544APWE4 executes a hardware power-on reset (POR) that initializes the internal control register to 0x00, deselecting all four channels. This occurs when VCC rises above VPORR (1.5 V typical) and ensures no downstream bus is inadvertently activated before the master issues a channel-select command. The POR also resets the I²C state machine, guaranteeing clean startup even after brownout events. The PCA9544APWE4 remains in this safe, all-channels-off state until explicitly configured via I²C write.

Can multiple PCA9544APWE4 devices share the same I²C bus?

Yes, up to eight PCA9544APWE4 devices can coexist on the same I²C bus using hardware-configurable addressing. Pins A0, A1, and A2 serve as binary address inputs - each tied to VCC or GND to set a unique 3-bit address extension, resulting in a full 7-bit slave address range from 0xE0 to 0xE7. This allows hierarchical bus expansion, such as deploying one PCA9544APWE4 per server blade or router line card while maintaining centralized control from a single master processor.