Texas Instruments PCA9546ADWG4

Overview

PCA9546ADWG4 from Texas Instruments is a low-voltage 4-channel bidirectional I²C and SMBus switch with active-low reset, designed to resolve slave address conflicts by routing master SCL/SDA to one or more of four downstream SCn/SDn channels. It operates from 2.3 V to 5.5 V, supports 0–400 kHz clock rates, enables voltage-level translation between 1.8-V, 2.5-V, 3.3-V, and 5-V buses, and features low R_ON (≤9 Ω at 5 V) for minimal signal degradation in server and telecom backplane applications.

For engineers reviewing the PCA9546ADWG4 datasheet, PCA9546ADWG4 pinout, PCA9546ADWG4 application, or PCA9546ADWG4 equivalent, this page delivers verified functional architecture, confirmed channel selection logic, validated voltage translation capability across all four channels, exact TSSOP-16 pin mapping, and real-world design implications for bus capacitance distribution and fault recovery via RESET.

Technical Context

The PCA9546ADWG4 implements a register-controlled 1-of-4 (or multi-channel) bidirectional pass-gate switch architecture, where channel enable states are stored in an 8-bit I²C-accessible control register with four LSBs (B0–B3) directly mapping to SC0/SD0 through SC3/SD3. Its internal power-on reset (POR) and external active-low RESET input both force all channels to deselect and clear the I²C state machine.

Each channel's data path uses voltage-limited pass gates referenced to VCC, enabling true bidirectional level translation without direction pins; external pull-up resistors on each SCn/SDn pair set local bus voltage (VDPU0–VDPU3), while SCL/SDA use VDPUM - allowing simultaneous operation of 1.8-V sensors and 5-V controllers on shared infrastructure.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm), thermally enhanced with exposed pad not connected internally; pinout validated per TI SCPS148G Rev G datasheet Figure 5 (D/DW package top view).

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9546ADWG4, the PCA9544APW offers half the channel count but identical voltage translation and reset functionality, while the TCA9544APWR provides second-source availability at the cost of lower ESD immunity - neither matches the 4-channel flexibility and 2000-V HBM protection of the original.

Availability

PCA9546ADWG4 is available at Aetrix Electronics and suitable for server baseboard management, telecom line card expansion, and industrial PLC I/O modules requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9546ADWG4 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 PCA9546ADWG4 belongs to TI's I²C switch and multiplexer product line, engineered specifically to solve I²C slave address conflicts and enable mixed-voltage interconnect in dense, high-reliability systems like servers and telecom infrastructure.

FAQ

What is the function of the RESET pin on the PCA9546ADWG4?

The RESET pin on the PCA9546ADWG4 is an active-low asynchronous input that forces the device to deselect all four channels and reset its internal I²C state machine. When asserted for ≥6 ns, it clears the control register and releases any stuck downstream bus condition - critical for recovering from I²C lockups in mission-critical systems. The PCA9546ADWG4 requires an external pull-up resistor on RESET to ensure proper initialization.

Can the PCA9546ADWG4 translate between 1.8-V and 5-V I²C buses?

Yes, the PCA9546ADWG4 supports bidirectional voltage-level translation between 1.8-V and 5-V I²C buses. This is achieved by setting VCC to the highest voltage present (e.g., 5 V), then using separate external pull-up resistors on each SCn/SDn pair tied to their respective domain voltages (VDPU0 = 1.8 V, VDPU1 = 5 V). The PCA9546ADWG4's pass-gate architecture ensures signal integrity without direction control pins.

How many PCA9546ADWG4 devices can be placed on the same I²C bus?

Up to eight PCA9546ADWG4 devices can coexist on a single I²C bus, enabled by three hardware-configurable address pins (A0, A1, A2). Each combination of A0–A2 ties sets a unique 7-bit slave address in the range 0x70 to 0x77. All PCA9546ADWG4 devices share the same control register format and respond only to their assigned address, preventing command collisions.

Does the PCA9546ADWG4 require external pull-up resistors on all I²C lines?

Yes, the PCA9546ADWG4 requires external pull-up resistors on all I²C lines: SDA and SCL (upstream, pulled to VDPUM), and each SCn/SDn pair (downstream, pulled to their respective VDPUx voltages). No internal pull-ups exist on address or RESET pins either - A0–A2 must be hard-wired to VCC or GND, and RESET requires a pull-up to VDPUM. This ensures precise voltage domain control and avoids contention.

What happens to the PCA9546ADWG4 channels during power-up?

During power-up, the PCA9546ADWG4 enters a power-on reset (POR) state until VCC reaches VPOR (1.6–2.1 V), after which all four channels remain deselected by default. This "no channel selected" state (control register = 0x00) prevents unintended bus activity and ensures clean initialization. The PCA9546ADWG4 maintains this safe state until the host processor writes a valid channel-enable value to the control register via I²C.