Texas Instruments PCA9548ADBG4

Overview

PCA9548ADBG4 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, and enables isolation of I²C slave address conflicts in multi-sensor systems. It is used in server motherboard management controllers to route SCL/SDA signals among eight independent downstream I²C buses.

For engineers reviewing the PCA9548ADBG4 datasheet, PCA9548ADBG4 pinout, PCA9548ADBG4 application, or PCA9548ADBG4 equivalent, key selection criteria include channel count, reset functionality, I²C timing compliance (Standard/Fast Mode), voltage translation capability across 1.8 V/2.5 V/3.3 V/5 V domains, and 24-pin SSOP package compatibility with thermal and layout constraints.

Technical Context

The PCA9548ADBG4 implements eight independent bidirectional pass-gate switches controlled via a single 8-bit I²C register, where each bit enables one SCn/SDn channel. Its internal state machine resets on power-up or RESET assertion, deselecting all channels and initializing I²C communication logic.

It supports voltage translation by allowing separate pull-up resistors on each channel - enabling interoperability between 1.8-V sensors and 5-V masters - while maintaining 5-V-tolerant inputs and low R_ON (≤10 Ω at 5 V) for minimal signal degradation. The device complies with I²C Standard Mode (100 kHz) and Fast Mode (400 kHz) timing requirements, including t_BUF, t_STDH, and C_b ≤ 400 pF.

Key Specifications

Pinout & Package

The PCA9548ADBG4 is packaged in a 24-pin SSOP (DB) package measuring 8.20 mm × 5.30 mm, with exposed thermal pad not present. Pin functions are validated per TI SCPS143G datasheet Figures 5-1 and Table 5-1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9548ADBG4, the TCA9548APWR offers identical functionality in a smaller TSSOP package but with reduced thermal performance, while the PCA9546ADW provides half the channel count in a compact SOIC-16 format - making it suitable for simpler topologies where full 8-channel capacity is unnecessary.

Availability

PCA9548ADBG4 is available at Aetrix Electronics and suitable for server management, industrial sensor hubs, and telecom switching equipment requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9548ADBG4 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, embedded processing, and connectivity technologies, with leadership in industrial, automotive, and communications markets.

The PCA9548A product line was designed to solve I²C bus contention and voltage-domain interoperability challenges in dense, multi-peripheral systems - targeting server, networking, and factory automation applications requiring reliable, software-configurable bus isolation.

FAQ

What is the maximum I²C clock frequency supported by the PCA9548ADBG4?

The PCA9548ADBG4 supports I²C Fast Mode operation up to 400 kHz, meeting timing requirements for t_SCH, t_SCL, and t_BUF across its full operating range (2.3 V to 5.5 V). It also fully complies with Standard Mode (100 kHz) specifications. This dual-mode capability ensures compatibility with legacy and high-speed I²C peripherals without protocol modification. The PCA9548ADBG4 maintains signal integrity through low R_ON and controlled propagation delay (<1 ns typical).

How does the PCA9548ADBG4 resolve I²C slave address conflicts?

The PCA9548ADBG4 resolves I²C slave address conflicts by providing eight physically isolated downstream I²C channels (SC0/SD0 to SC7/SD7). Each channel can host identical slave devices (e.g., multiple TMP102 sensors), and the master selects only one channel at a time via the 8-bit control register. This prevents address collisions because slaves on unselected channels are electrically disconnected from the bus. The PCA9548ADBG4 ensures deterministic arbitration-free communication without requiring slave firmware changes or external multiplexing logic.

Can the PCA9548ADBG4 translate between different I²C voltage levels?

Yes, the PCA9548ADBG4 enables voltage-level translation between 1.8 V, 2.5 V, 3.3 V, and 5 V I²C domains. This is achieved by using separate external pull-up resistors on each SCn/SDn channel, tied to their respective domain's supply voltage. The VCC pin sets the maximum high-level voltage passed through the switch, while all I/O pins are 5-V tolerant. No additional level-shifting components are required. The PCA9548ADBG4 maintains signal integrity across domains due to low R_ON and controlled capacitive loading.

What happens to the PCA9548ADBG4 channels during power-up or RESET assertion?

During power-up, the PCA9548ADBG4 performs a power-on reset (POR) that deselects all eight channels and initializes the I²C state machine to its default condition. Similarly, asserting the active-low RESET pin for ≥6 ns causes identical behavior: all channel bits clear, the control register resets to 0x00, and the upstream SCL/SDA lines are disconnected from all downstream channels. This ensures safe, predictable startup and fault recovery. The PCA9548ADBG4 guarantees no glitch on power-up and supports hot insertion without bus lockup.

How many PCA9548ADBG4 devices can share the same I²C bus?

Up to eight PCA9548ADBG4 devices can share the same I²C bus, enabled by three hardware address pins (A0, A1, A2). Each pin can be tied to VCC or GND, yielding eight unique 7-bit slave addresses (0x70 to 0x77). This allows hierarchical I²C expansion - for example, one PCA9548ADBG4 managing eight sensor groups, each with its own downstream PCA9548ADBG4. Address configuration is static and must remain stable between START and STOP conditions during I²C transactions. The PCA9548ADBG4 supports standard I²C arbitration and ACK/NACK protocols without modification.