Texas Instruments PCA9543APWR

Overview

PCA9543APWR from Texas Instruments is a 2-channel bidirectional I²C bus switch with interrupt logic and active-low reset, supporting Standard-Mode (100 kHz) and Fast-Mode (400 kHz) operation, voltage-level translation between 1.8-V/2.5-V/3.3-V and 5-V buses, and dual independent channel selection via an 8-bit I²C control register - used in server backplanes to isolate I²C slave address conflicts among identical temperature sensors.

For engineers reviewing the PCA9543APWR datasheet, PCA9543APWR pinout, PCA9543APWR application, or PCA9543APWR equivalent, key selection considerations include its dual-channel interrupt arbitration (INT0/INT1 → open-drain INT), 2.3-V to 5.5-V supply range, 5.5-V tolerant I/Os, low 7–25 Ω on-state resistance, and TSSOP-14 package compatibility with space-constrained industrial control modules.

Technical Context

The PCA9543APWR implements a master-controlled, register-based switching architecture where SCL/SDA upstream signals fan out to two downstream SCn/SDn pairs; channel enable states (B0/B1 bits) and interrupt status (INT0/INT1 bits) are stored in a single 8-bit read/write control register accessible via standard I²C protocol.

Its interrupt logic performs a wired-AND of INT0 and INT1 inputs onto the open-drain INT output, enabling centralized interrupt detection without polling; the active-low RESET input forces both channels deselected and resets the I²C state machine, recovering stuck-bus conditions independently of power cycling.

Key Specifications

Pinout & Package

TSSOP-14 package (5.00 mm × 4.40 mm body size), 14-pin surface-mount, lead-free and RoHS-compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9544APWR and PCA9546APWR, the PCA9543APWR delivers optimal cost-performance balance for dual-channel isolation, offering identical interrupt logic and voltage translation with minimal footprint and no over-provisioned features.

Availability

PCA9543APWR is available at Aetrix Electronics and suitable for server backplane management, rack-mount telecom switching, and factory automation PLC I/O modules requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9543APWR 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 technologies, with decades of I²C interface innovation and broad industrial qualification.

The PCA9543APWR belongs to TI's I²C switch and multiplexer product line, designed specifically to resolve bus contention, slave address conflicts, and mixed-voltage interoperability in dense embedded systems.

FAQ

What is the function of the RESET pin on the PCA9543APWR?

The RESET pin on the PCA9543APWR is an active-low asynchronous input that forces the internal control register to 0x00 and deselects both I²C channels, resetting the I²C state machine to recover from downstream bus lockup. It requires a minimum 4 ns low pulse and must be pulled up to VCC when unused. This function is fully independent of power cycling and is essential for robust field operation in servers and telecom gear where bus faults cannot trigger system reboot.

How does the PCA9543APWR handle voltage-level translation between different I²C buses?

The PCA9543APWR uses VCC-referenced pass gates to enable voltage-level translation: upstream SDA/SCL operate at master voltage (e.g., 3.3 V), while SD0/SC0 and SD1/SC1 can each be pulled up to independent voltages (e.g., 1.8 V, 2.5 V, or 5 V) via external resistors. All I/O pins are 5.5-V tolerant, eliminating external level shifters. This allows a 3.3-V microcontroller to safely communicate with both 1.8-V accelerometers and 5-V EEPROMs through the same PCA9543APWR device.

Can the PCA9543APWR be used with more than two I²C slave devices per channel?

Yes - the PCA9543APWR does not limit the number of slaves per channel; it only isolates the bus segments electrically. Each downstream channel (SC0/SD0 or SC1/SD1) can support multiple I²C slaves, provided total bus capacitance remains ≤400 pF and address conflicts are resolved externally. The device's role is segmentation, not arbitration; thus, standard I²C rules (pull-up sizing, slew rate, clock stretching) still apply within each channel.

What happens to the PCA9543APWR's control register after power-on or RESET assertion?

Upon power-on or RESET assertion, the PCA9543APWR's 8-bit control register resets to 0x00 - deselecting both channels (B0 = B1 = 0), clearing interrupt flags (INT0 = INT1 = 0), and disabling all downstream paths. This default state prevents bus contention during system startup and ensures predictable initialization. The register remains at 0x00 until the master writes a new value via the I²C interface, making the PCA9543APWR inherently fail-safe.

How do the INT0 and INT1 pins interact with the shared INT output on the PCA9543APWR?

INT0 and INT1 are active-low interrupt inputs tied to separate downstream I²C channels; the PCA9543APWR internally performs a wired-AND operation, driving the open-drain INT output low whenever either INT0 or INT1 is asserted. This allows a single MCU GPIO to monitor interrupts from both channels. To identify the source, the master reads the control register: bit 4 reflects INT0 status and bit 5 reflects INT1 status - enabling precise fault localization without additional hardware.