NXP Semiconductors PCA9541BS/01,118

Overview

PCA9541BS/01 from NXP Semiconductors is a 2-to-1 bidirectional I²C-bus master selector with interrupt logic and reset, designed for high-reliability dual-master systems where uninterrupted communication must persist during master failure or hot-swap maintenance. It features channel 0 selected at power-up, active LOW reset, dual active LOW interrupt outputs (INT0/INT1), and bus recovery initialization. It enables failover control between two upstream masters sharing downstream I²C slave devices in telecom infrastructure and industrial control systems.

For engineers reviewing the PCA9541BS/01 datasheet, PCA9541BS/01 pinout, PCA9541BS/01 application, or PCA9541BS/01 equivalent, key selection criteria include its HVQFN16 package, 2.3 V to 5.5 V supply range, 0 Hz–400 kHz I²C operation, voltage-level translation capability (1.8 V/2.5 V/3.3 V ↔ 5 V), and bus traffic sensing with configurable interrupt masking.

Technical Context

The PCA9541BS/01 implements a deterministic, non-arbitrated channel switching mechanism controlled via I²C writes to dedicated CONTROL registers per master, with state updates synchronized to STOP conditions. Its internal bus sensor detects non-idle downstream conditions during switching and triggers BUSOK interrupts when bus initialization is disabled.

It integrates independent interrupt enable (IE) and status (ISTAT) registers for each master, supporting masked/unmasked reporting of BUSLOST, BUSOK, and BUSINIT events. The device uses an internal oscillator for nine-clock pulse bus recovery, followed by NACK and STOP, ensuring slave devices enter a known initialized state before channel handover.

Key Specifications

Pinout & Package

HVQFN16 package: plastic thermal-enhanced very thin quad flat package, 4 mm × 4 mm × 0.85 mm body, 16 terminals, exposed thermal pad (VSS-connected) requiring PCB soldering for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9541PW/01 and PCA9541D/01, the PCA9541BS/01 delivers superior thermal dissipation and board-area efficiency in space-constrained, high-reliability applications-making it optimal for telecom, medical, and embedded systems requiring long-term stability under continuous operation.

Availability

PCA9541BS/01 is available at Aetrix Electronics and suitable for telecom infrastructure, industrial PLC redundancy, and medical diagnostic equipment requiring stable component supply across extended product lifecycles.

Supply support for PCA9541BS/01 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 company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT markets.

The PCA9541 series belongs to NXP's I²C-bus infrastructure portfolio, engineered specifically for fault-tolerant dual-master systems where bus continuity, deterministic failover, and mixed-voltage interoperability are mission-critical.

FAQ

What is the power-up behavior of the PCA9541BS/01?

The PCA9541BS/01 powers up with Channel 0 selected by default, connecting master 0 to the downstream I²C bus. This behavior is hardwired into the /01 variant and ensures immediate operational readiness of the primary controller without software initialization. The internal Power-On Reset (POR) circuit guarantees consistent startup state, and the RESET pin provides synchronous override capability during runtime.

How does the PCA9541BS/01 handle bus recovery during channel switching?

The PCA9541BS/01 supports two bus recovery modes: automatic initialization (enabled via BUSINIT bit) and traffic-sensing alert (BUSOK). When BUSINIT = 1, it sends nine SCL pulses, releases SDA_SLAVE (equivalent to NACK), then issues a STOP to reset downstream slaves before switching. If BUSINIT = 0 and bus traffic is detected, it asserts BUSOK to signal external recovery is needed - ensuring slave devices remain responsive regardless of master state.

Can the PCA9541BS/01 translate between different I²C voltage domains?

Yes, the PCA9541BS/01 enables voltage-level translation between 1.8 V, 2.5 V, 3.3 V, and 5 V I²C buses using its VDD-referenced pass-gate architecture. The maximum passed high voltage is limited by VDD, so connecting VDD to 3.3 V allows 3.3 V masters to safely communicate with 5 V slaves. No external components are required, and all I/O pins are 6.0 V tolerant for robust interfacing.

What is the function of the INT_IN pin on the PCA9541BS/01?

The INT_IN pin on the PCA9541BS/01 is an active LOW interrupt input that collects asynchronous interrupt signals from downstream I²C slaves (e.g., temperature alerts or fault flags) and propagates them to both upstream masters via INT0 and INT1 when enabled. It supports daisy-chained monitoring and can be masked per master using the INTINMSK bit in the IE register, preserving system-level interrupt prioritization.

Does the PCA9541BS/01 require external pull-up resistors on all I²C lines?

Yes, the PCA9541BS/01 requires external pull-up resistors on all I²C lines - SCL_MST0, SDA_MST0, SCL_MST1, SDA_MST1, SCL_SLAVE, SDA_SLAVE, INT0, INT1, and INT_IN - because it contains no internal pull-ups. Resistor values must be selected based on bus capacitance and speed (e.g., 2.2 kΩ for 400 kHz at ≤400 pF), and all I/O pins are 6.0 V tolerant to accommodate mixed-voltage designs.