Texas Instruments PCA9546APWTG4

Overview

PCA9546APWTG4 from Texas Instruments is a low-voltage 4-channel bidirectional I²C/SMBus switch with active-low reset, used to resolve slave address conflicts and enable voltage-level translation between 1.8-V, 2.5-V, 3.3-V, and 5-V buses. It features four independent SCn/SDn channels, programmable channel selection via I²C control register, and operates across 2.3 V to 5.5 V supply range.

For engineers reviewing the PCA9546APWTG4 datasheet, PCA9546APWTG4 pinout, PCA9546APWTG4 application, or PCA9546APWTG4 equivalent, this device supports fast-mode (400 kHz) and standard-mode (100 kHz) I²C operation, provides latch-up immunity (>100 mA), ESD protection (±2000-V HBM), and enables selective isolation of downstream I²C segments in high-density server and telecom systems.

Technical Context

The PCA9546APWTG4 implements a master-controlled, register-based switching architecture where the upstream SDA/SCL pair fans out to four downstream SCn/SDn channels. Channel selection is determined by the four LSBs of an 8-bit I²C-accessible control register, supporting any combination of enabled channels-including simultaneous activation-subject to bus capacitance limits.

Its internal pass-gate design uses VCC as a voltage-limiting reference to enable bidirectional level translation without external logic. The active-low RESET input directly resets the I²C state machine and deselects all channels, while power-on reset ensures default deselected state at VPOR ≥ 1.6 V.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm), thermally optimized for surface-mount assembly in space-constrained server and networking PCBs.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9544APW and TCA9544APWR, the PCA9546APWTG4 uniquely delivers four independently controllable channels plus hardware reset in a single TSSOP-16 footprint-enabling scalable I²C topology management without cascading switches or compromising bus reliability.

Availability

PCA9546APWTG4 is available at Aetrix Electronics and suitable for server management subsystems, telecom router backplanes, and factory automation PLC I/O modules requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9546APWTG4 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 headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and communications markets.

The PCA9546A product line was designed specifically to solve I²C slave address conflicts and bus capacitance overload in dense multi-peripheral systems-targeting servers, routers, and programmable logic controllers where reliable, software-controllable bus segmentation is critical.

FAQ

What is the function of the RESET pin on the PCA9546APWTG4?

The RESET pin on the PCA9546APWTG4 is an active-low input that forces the internal I²C state machine to reset and deselects all four channels immediately upon assertion. It recovers the device from stuck-bus conditions on any downstream SCn/SDn pair. The PCA9546APWTG4 requires a minimum pulse width of 6 ns and must be pulled up externally to VCC. Unlike power cycling, RESET preserves VCC stability and enables rapid fault recovery without system interruption.

How many PCA9546APWTG4 devices can share the same I²C bus?

Up to eight PCA9546APWTG4 devices can operate on the same I²C bus, enabled by three hardware-configurable address pins (A0, A1, A2). Each pin must be tied to either VCC or GND to set a unique 3-bit slave address. This addressing scheme allows hierarchical bus expansion-for example, one PCA9546APWTG4 per blade in a modular server chassis-without requiring additional I²C controllers or address translation logic.

Does the PCA9546APWTG4 support voltage-level translation between different I²C domains?

Yes, the PCA9546APWTG4 supports bidirectional voltage-level translation by leveraging its VCC-referenced pass-gate architecture. When VCC is set to an intermediate value (e.g., 3.3 V), it limits the maximum voltage passed from higher-voltage domains (e.g., 5-V SDA) to lower-voltage slaves (e.g., 1.8-V SD0), provided each SCn/SDn pair uses dedicated pull-up resistors to its local VDPUx. This eliminates external level shifters while maintaining I²C timing compliance across mixed-supply systems.

What happens to the PCA9546APWTG4 channels during power-up?

During power-up, the PCA9546APWTG4 enters a power-on reset (POR) state until VCC rises above VPOR (1.6 V min). At that point, the internal control register initializes to 0x00, deselecting all four channels. This "no glitch" behavior ensures no unintended channel activation occurs before firmware configures the device. The PCA9546APWTG4 remains in this safe default state regardless of I²C bus activity, preventing false starts or contention on downstream segments.

Can multiple channels of the PCA9546APWTG4 be enabled simultaneously?

Yes, the PCA9546APWTG4 allows any combination of its four channels (0–3) to be enabled simultaneously via the four LSBs of its 8-bit control register. For instance, writing 0x0F selects all channels, while 0x05 enables channels 0 and 2 only. However, simultaneous activation increases total bus capacitance; designers must verify cumulative load remains ≤400 pF per segment and adjust pull-up resistor values accordingly to maintain rise/fall time compliance at target clock frequencies.