Texas Instruments PCA9546APWRG4

Overview

PCA9546APWRG4 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 from 2.3 V to 5.5 V supply.

For engineers reviewing the PCA9546APWRG4 datasheet, PCA9546APWRG4 pinout, PCA9546APWRG4 application, or PCA9546APWRG4 equivalent, this device supports fast-mode (400 kHz) and standard-mode (100 kHz) I²C operation, provides latch-up immunity >100 mA, offers 5.5-V tolerant inputs, and enables hot insertion in multi-sensor server and telecom systems.

Technical Context

The PCA9546APWRG4 implements a quad-channel I²C bus switch with independent bidirectional pass-gate control per channel (SC0/SD0–SC3/SD3), managed by an 8-bit I²C-accessible control register where bits B0–B3 directly enable/disable each channel. Its internal power-on reset (VPOR = 1.6–2.1 V) and external active-low RESET input both force deselection of all channels and reset the I²C state machine.

Switch architecture uses VCC-referenced pass gates to limit maximum output voltage (Vpass), enabling voltage translation without level shifters. Each channel's SDA/SC line requires an external pull-up resistor tied to its respective VDPUx rail-allowing mixed-voltage communication while maintaining I²C timing compliance up to 400 kHz with ≤400 pF bus capacitance.

Key Specifications

Pinout & Package

TSSOP-16 package (5.00 mm × 4.40 mm), lead-free and RoHS-compliant, optimized for high-density PCB layouts in space-constrained embedded systems.

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 PCA9546APWRG4 delivers double the channel count and critical bus-recovery functionality - making it the only option for 4-sensor address resolution or mixed-voltage systems requiring guaranteed fault recovery without host intervention.

Availability

PCA9546APWRG4 is available at Aetrix Electronics and suitable for server management, telecom router backplanes, and industrial PLC I/O expansion requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant packaging.

Supply support for PCA9546APWRG4 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 expertise in I²C infrastructure and power-efficient interface solutions.

The PCA9546A product line was designed specifically for high-reliability I²C bus segmentation in dense, multi-peripheral systems - addressing slave address conflicts, voltage translation, and bus fault recovery in servers, networking gear, and industrial controls.

FAQ

What is the function of the RESET pin on the PCA9546APWRG4?

The RESET pin on the PCA9546APWRG4 is an active-low asynchronous input that forces deselection of all four channels and resets the internal I²C state machine. When asserted for ≥6 ns, it recovers the device from stuck-bus conditions - such as a downstream SDA line held low - without requiring a power cycle. The pin must be pulled up to VCC (not VDPUM) to prevent current injection into the supply rail, as documented in the RESET Errata section of the datasheet.

Can the PCA9546APWRG4 translate between 1.8-V and 5-V I²C buses?

Yes, the PCA9546APWRG4 supports voltage-level translation between 1.8-V, 2.5-V, 3.3-V, and 5-V I²C buses. Its pass-gate architecture uses VCC to clamp maximum output voltage (Vpass), allowing each SCn/SDn channel to operate with its own pull-up voltage (VDPUx). For example, with VCC = 3.3 V, a 1.8-V sensor on Channel 0 and a 5-V EEPROM on Channel 2 can both communicate correctly with a 3.3-V master - provided each channel has its dedicated pull-up resistor tied to its respective VDPUx rail.

How many PCA9546APWRG4 devices can share the same I²C bus?

Up to eight PCA9546APWRG4 devices can share the same I²C bus, enabled by three hardware-configurable address pins (A0, A1, A2). Each pin connects to either VCC or GND to set a unique 3-bit address extension, resulting in slave addresses from 0x70 to 0x77. This allows hierarchical bus expansion - for instance, one PCA9546APWRG4 managing four temperature sensors per board, with eight boards daisy-chained via distinct addresses on a common backplane I²C bus.

Does the PCA9546APWRG4 support Fast-Mode I²C (400 kHz)?

Yes, the PCA9546APWRG4 fully supports Fast-Mode I²C operation up to 400 kHz, as verified in Section 6.5 of the datasheet. Its propagation delay is ≤1 ns (with CL = 50 pF), and it meets all Fast-Mode timing requirements including tsch ≥0.6 µs, tscl ≥1.3 µs, and tbuf ≥1.3 µs. The device maintains signal integrity across all four channels simultaneously, provided total bus capacitance per segment remains ≤400 pF and pull-up resistors are sized appropriately for target rise time.

What happens to the channels during power-up of the PCA9546APWRG4?

During power-up, the PCA9546APWRG4 enters a power-on reset (POR) state when VCC rises above VPOR (1.6–2.1 V), holding all channels deselected until reset release. This guarantees no unintended I²C traffic passes through any channel before firmware initializes the control register. The default state after POR is B3–B0 = 0000 - meaning all four channels (0–3) remain open-circuit until explicitly enabled via I²C write. This behavior prevents glitches, false starts, or contention on downstream buses during system boot.