Texas Instruments PCA9548ADB

Overview

PCA9548A from Texas Instruments is an 8-channel bidirectional I²C bus switch with voltage-level translation, active-low reset, and hardware address selection (A0–A2). It operates from 2.3 V to 5.5 V, supports up to 400 kHz clock frequency, features <10 Ω typical R_ON, and resolves slave address conflicts in multi-sensor systems.

For engineers reviewing the PCA9548A datasheet, PCA9548A pinout, PCA9548A application, or PCA9548A equivalent, this device is selected for I²C bus expansion, level-shifting between 1.8-V/2.5-V/3.3-V and 5-V domains, hot-insertion support, and fault recovery via hardware reset-critical in server backplanes and industrial sensor hubs.

Technical Context

The PCA9548A implements eight independent bidirectional pass-gate switches controlled by a single 8-bit I²C register, enabling any combination of channels (0–7) to be selected simultaneously. Its internal state machine resets on power-up or RESET assertion, deselecting all channels and initializing I²C logic.

Each SCn/SDn channel supports independent voltage translation via external pull-up resistors tied to local bus voltages; all I/O pins are 5-V tolerant, and the VCC pin sets the maximum high-voltage pass-through limit. The device complies with I²C Standard-Mode (100 kHz) and Fast-Mode (400 kHz) timing requirements.

Key Specifications

Pinout & Package

PCA9548A is available in multiple 24-pin packages including SSOP (DB), TVSOP (DGV), SOIC (DW), TSSOP (PW), and VQFN (RGE); all share identical pin function mapping and 5-V-tolerant I/O structure.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9548A, TCA9548A offers superior ESD protection and lower operating current while maintaining full functional and pin compatibility; PCA9546APW reduces channel count and removes RESET but fits identical PCB footprints-making it a layout-compatible downgrade for simpler topologies.

Availability

PCA9548A is available at Aetrix Electronics and suitable for server backplanes, industrial sensor hubs, and telecom router management buses requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9548A 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 company specializing in analog and embedded processing technologies, with leadership in interface, power management, and signal chain solutions.

The PCA9548A belongs to TI's I²C infrastructure portfolio, designed specifically to solve bus contention, voltage translation, and scalability challenges in multi-slave embedded systems - especially in data center, industrial automation, and communications equipment.

FAQ

What is the primary function of the PCA9548A?

The PCA9548A is an 8-channel bidirectional I²C bus switch that enables a single I²C master to communicate with multiple downstream slave devices on isolated channels. It resolves slave address conflicts, supports voltage-level translation between 1.8-V, 2.5-V, 3.3-V, and 5-V domains, and includes an active-low RESET input for fault recovery - all critical functions in dense I²C systems like servers and sensor hubs. The PCA9548A achieves this using a single 8-bit control register accessed via the upstream I²C bus.

Does the PCA9548A support Fast-Mode I²C operation?

Yes, the PCA9548A fully supports Fast-Mode I²C operation up to 400 kHz, meeting all timing requirements specified in the I²C specification for both standard and fast modes. Its propagation delay is under 1 ns (at CL = 50 pF), and its low R_ON (<10 Ω typical) ensures signal integrity across the full frequency range. The PCA9548A also supports Standard-Mode (100 kHz) and handles bus capacitance up to 400 pF - making it suitable for high-density routing in routers and industrial controllers.

How does the PCA9548A handle voltage-level translation between different I²C domains?

The PCA9548A enables voltage-level translation by allowing independent pull-up resistors on each SCn/SDn channel, tied to their respective local supply voltages (e.g., 1.8 V for sensors, 5 V for master). Its pass-gate architecture and 5-V-tolerant I/O pins ensure signals pass unidirectionally or bidirectionally without clamping or distortion. The VCC pin defines the maximum high-voltage threshold, and all I/Os operate safely across 2.3 V to 5.5 V - so the PCA9548A itself acts as a passive, configurable level shifter without external components.

What happens to the PCA9548A channels during power-up or RESET assertion?

On power-up, the PCA9548A performs a power-on reset (POR) that deselects all eight channels and initializes the I²C state machine to default values - ensuring no unintended bus connections. Similarly, asserting the active-low RESET pin (≥6 ns pulse width) forces immediate deselection of all channels and reinitializes internal logic, recovering from stuck-bus conditions without power cycling. Both events guarantee safe, deterministic startup behavior - a key reliability feature in the PCA9548A for mission-critical applications.

Can multiple PCA9548A devices share the same I²C bus?

Yes, up to eight PCA9548A devices can coexist on the same upstream I²C bus using the three hardware address pins (A0, A1, A2), which configure a 3-bit slave address ranging from 0x70 to 0x77. Each device operates independently, allowing hierarchical bus expansion - for example, one PCA9548A managing sensor clusters and another handling power ICs - all controlled by the same master. This scalability is a core design feature of the PCA9548A and eliminates address collision issues in complex embedded systems.