Texas Instruments PCA9544APW

Overview

PCA9544APW from Texas Instruments is a low-voltage, 4-channel bidirectional I²C/SMBus multiplexer with integrated interrupt logic and voltage-level translation. It enables one master to selectively route SCL/SDA signals to one of four downstream slave buses, supports 1.8-V to 5-V bus interoperability, features active-low interrupt aggregation (INT = INT3 ∧ INT2 ∧ INT1 ∧ INT0), and operates from 2.3 V to 5.5 V at up to 400 kHz - used in server backplanes to resolve I²C slave address conflicts among identical temperature sensors.

For engineers reviewing the PCA9544APW datasheet, PCA9544APW pinout, PCA9544APW application, or PCA9544APW equivalent, this page delivers verified technical context, real-world design meaning for key specs, validated TSSOP-20 pin functions, confirmed voltage translation behavior, and two rigorously cross-checked alternative multiplexers for I²C bus expansion in telecom and industrial control systems.

Technical Context

The PCA9544APW implements a single-control-register architecture where three LSBs select exactly one of four bidirectional switch channels (SCn/SDn), while four MSBs reflect real-time interrupt status from each channel. Its pass-gate design uses VCC as a voltage clamp, enabling level-shifting without external translators - e.g., 3.3-V master communicates with 5-V slaves via independent pull-up networks per channel.

Interrupt logic performs wired-AND aggregation: any active-low INTn input forces active-low INT output, with 4 µs valid delay and 2 µs reset delay. Power-on reset initializes all channels deselected and clears the I²C state machine when VCC rises above 1.5 V (VPORR), ensuring glitch-free startup and recovery from stuck-bus faults.

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 PCA9544APW, TCA9544APWR offers lower standby current for energy-sensitive applications, while PCA9548APW provides double the channel count in a pin-compatible footprint upgrade path - both retain identical interrupt behavior, voltage translation capability, and I²C timing compliance.

Availability

PCA9544APW is available at Aetrix Electronics and suitable for server backplanes, telecom routers, and factory automation systems requiring stable component supply, long-term lifecycle assurance, and guaranteed traceable sourcing.

Supply support for PCA9544APW 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 for industrial, automotive, and communications markets.

The PCA9544APW belongs to TI's I²C infrastructure portfolio, designed specifically to solve bus contention, voltage mismatch, and interrupt aggregation challenges in dense, multi-peripheral embedded systems.

FAQ

What is the maximum clock frequency supported by the PCA9544APW?

The PCA9544APW supports Standard-mode I²C up to 100 kHz and Fast-mode I²C up to 400 kHz, as specified in Section 6.6 of the datasheet. Its switching characteristics (tpd ≤ 1 ns at CL = 50 pF) ensure signal integrity within these limits, making PCA9544APW suitable for high-speed sensor polling in real-time control loops without introducing timing violations.

Does the PCA9544APW require external pull-up resistors on all I²C lines?

Yes, the PCA9544APW requires external pull-up resistors on all SDA/SCL lines: upstream (SCL, SDA), downstream (SC0–SC3, SD0–SD3), and interrupt lines (INT0–INT3, INT). Each set must be pulled to its respective voltage domain (VDPUM for master, VDPU0–VDPU3 for slaves) - no internal pull-ups exist, so omitting them will prevent proper I²C bus operation and cause PCA9544APW communication failure.

Can multiple PCA9544APW devices share the same I²C bus?

Yes, up to eight PCA9544APW devices can coexist on one I²C bus using the A0, A1, and A2 address pins to configure unique 7-bit slave addresses. Each pin must be hard-wired to VCC or GND - floating address pins are undefined and will cause bus collisions. This enables scalable I²C expansion in systems like modular telecom chassis where PCA9544APW units manage distinct functional zones.

How does the PCA9544APW handle voltage translation between different I²C domains?

The PCA9544APW achieves voltage translation by using VCC as a pass-gate threshold reference: signals passing through enabled channels are clamped to VCC, while external pull-up resistors on each SCn/SDn pair set the actual logic-high level (e.g., 3.3 V on SC0/SD0, 5 V on SC3/SD3). This allows PCA9544APW to interconnect 1.8-V, 2.5-V, 3.3-V, and 5-V I²C segments without additional components - verified by Vpass measurements across supply ranges in Section 6.5.

What happens to the PCA9544APW channels during power-up?

On power-up, the PCA9544APW's internal power-on reset circuit holds the device in reset until VCC exceeds VPORR (1.5 V typical). Upon release, all channels are deselected by default, the control register resets to 0x00, and the I²C state machine initializes - ensuring no downstream bus is inadvertently activated. This behavior prevents bus contention and guarantees predictable startup, a critical requirement for PCA9544APW deployment in unattended industrial equipment.