NXP Semiconductors PCA9546AD,112

Overview

PCA9546AD,112 from NXP Semiconductors is a quad-channel bidirectional I²C-bus switch with active-low reset, operating from 2.3 V to 5.5 V supply, supporting up to 400 kHz clock frequency and enabling voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses. It serves as an upstream-to-downstream bus multiplexer in multi-peripheral I²C systems, such as server baseboard management controllers (BMCs) managing multiple sensor or EEPROM subsystems.

For engineers reviewing the PCA9546AD,112 datasheet, PCA9546AD,112 pinout, PCA9546AD,112 application, or PCA9546AD,112 equivalent, key selection criteria include channel-selectable isolation, 5 V-tolerant I/O, low Ron (5–30 Ω), reset recovery from stuck-bus faults, and SO16 package compatibility with legacy board layouts.

Technical Context

The PCA9546AD,112 implements four independent pass-gate switches controlled via an 8-bit I²C slave register where bits B0–B3 enable/disable SCx/SDx channels individually or in combination. Its internal power-on reset (POR) and external active-low RESET input both force all channels to deselected state, ensuring deterministic startup and fault recovery.

Switch operation relies on VDD-referenced pass transistors that clamp downstream high-level voltage (Vo(sw)) - e.g., Vo(sw) ≤ 2.8 V at VDD = 3.6 V - enabling safe level translation without external clamping diodes. All I/O pins are 5 V tolerant, and input capacitance is ≤13 pF per SDA/SCL line, preserving I²C timing margins up to 400 kHz Fast-mode.

Key Specifications

Pinout & Package

PCA9546AD,112 uses the SO16 (SOT109-1) plastic small outline package: 16-pin, 3.9 mm body width, 1.27 mm pitch, surface-mount, lead-free compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9548APWR and PCA9544AD,112, the PCA9546AD,112 uniquely balances 400 kHz Fast-mode operation, hardware reset, and SO16 compatibility - making it optimal for industrial and telecom systems requiring deterministic fault recovery and mixed-voltage interoperability without layout changes.

Availability

PCA9546AD,112 is available at Aetrix Electronics and suitable for server baseboard management, industrial sensor hubs, and telecom line card monitoring requiring stable component supply, long-term lifecycle assurance, and consistent SO16 packaging.

Supply support for PCA9546AD,112 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

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in interface and power management ICs.

The PCA9546A family was designed specifically to solve I²C bus contention and voltage-domain mismatch in dense, multi-peripheral embedded systems - delivering configurable isolation, robust reset, and seamless level translation in compact packages.

FAQ

What is the maximum I²C clock frequency supported by the PCA9546AD,112?

The PCA9546AD,112 supports I²C clock frequencies up to 400 kHz in Fast-mode operation. This is validated across its full operating voltage range (2.3 V to 5.5 V) and ambient temperature range (−40 °C to +85 °C), with timing parameters including tSU;DAT ≥100 ns and tLOW ≥1.3 μs meeting I²C Fast-mode specifications. The PCA9546AD,112 maintains signal integrity through low input capacitance (≤13 pF) and low Ron (5–30 Ω).

How does the PCA9546AD,112 handle voltage translation between different I²C bus domains?

The PCA9546AD,112 uses VDD-referenced pass-gate transistors to clamp downstream high-level voltage (Vo(sw)). For example, with VDD = 3.3 V, Vo(sw) is limited to ≤2.8 V, enabling safe communication between a 5 V upstream master and 3.3 V or 2.7 V downstream peripherals. External pull-up resistors on each SDx/SCx pair set the final logic-high level, eliminating need for discrete level shifters. The PCA9546AD,112 achieves this while maintaining 5 V tolerance on all I/O pins.

Does the PCA9546AD,112 require external pull-up resistors on its I²C lines?

Yes, the PCA9546AD,112 requires external pull-up resistors on all I²C lines: upstream SDA and SCL, and each downstream SDx and SCx pair. No internal pull-ups are integrated. Resistor values depend on bus capacitance and speed - e.g., 2.2 kΩ for 100 kHz Standard-mode or 1 kΩ for 400 kHz Fast-mode with ≤400 pF total load. Pull-ups must connect to the appropriate voltage rail for each segment (e.g., 3.3 V for downstream, 5 V for upstream), as specified in the PCA9546AD,112 application design-in guidelines.

What happens to the PCA9546AD,112 channels during power-up or reset?

During power-up, the PCA9546AD,112's internal power-on reset (POR) holds the device in reset until VDD exceeds VPOR (1.6–2.1 V), then initializes the control register to 00h - deselecting all four channels. Similarly, asserting the RESET pin LOW forces immediate deselection of all channels and resets the I²C state machine. Both mechanisms ensure no downstream bus is inadvertently enabled before firmware configuration, preventing address collisions or unintended peripheral access. This behavior is guaranteed for every PCA9546AD,112 power cycle or reset event.

Can multiple PCA9546AD,112 devices share the same I²C bus?

Yes, up to eight PCA9546AD,112 devices can coexist on a single I²C bus using hardware address pins A0, A1, and A2. These three pins configure the three LSBs of the fixed 7-bit slave address (1110A2A1A0), yielding addresses from 0xE0 to 0xE7. Since no internal pull-ups exist on A0–A2, each pin must be externally tied HIGH or LOW to establish a unique, non-floating address. This addressing scheme enables scalable I²C tree topologies without address conflicts - a core capability of the PCA9546AD,112.