NXP Semiconductors PCA9541D/03,112

Overview

The PCA9541D/03,112 from NXP Semiconductors is a 2-to-1 bidirectional I²C-bus master selector IC designed for high-reliability dual-master systems requiring failover operation without bus disruption. It features no-channel-selected-at-power-up behavior, active-low reset and interrupt logic, bus recovery initialization (9-clock + NACK + STOP), and voltage-level translation across 1.8 V to 5 V domains. It enables hot-swappable controller redundancy in telecom line cards and industrial PLC backplanes.

For engineers reviewing the PCA9541D/03,112 datasheet, PCA9541D/03,112 pinout, PCA9541D/03,112 application, or PCA9541D/03,112 equivalent, key selection criteria include power-up channel state (unselected), bus sensor-triggered external recovery signaling, dual-interrupt output routing (INT0/INT1), 4-bit hardware address configuration, and SO16 package compatibility with 2.3–5.5 V supply operation.

Technical Context

The PCA9541D/03,112 implements a deterministic, non-arbitrated channel switching mechanism controlled via I²C writes to per-master CONTROL registers (Reg#01), where MYBUS/NMYBUS bits indicate bus ownership and BUSON/NBUSON bits control physical connection state. Switching occurs only on receipt of a STOP condition from the requesting master.

Its internal bus sensor detects non-idle downstream conditions during channel transitions and asserts BUSOK interrupt if bus initialization is disabled; when enabled, it autonomously executes a 9-clock pulse sequence followed by NACK and STOP to reset slave devices before connecting the new master - all without requiring slave-side hardware reset pins.

Key Specifications

Pinout & Package

PCA9541D/03,112 is supplied in SO16 (SOT109-1) package: plastic small outline, 16 leads, 3.9 mm body width, lead pitch 1.27 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9544ADPW,118 and TCA9544APWR, the PCA9541D/03,112 uniquely delivers deterministic dual-master failover with autonomous bus initialization - eliminating software dependency for slave reset and reducing system-level validation effort in safety-critical or telecom applications.

Availability

PCA9541D/03,112 is available at Aetrix Electronics and suitable for telecom line card redundancy, industrial PLC backplanes, and server BMC failover systems requiring stable component supply, long-term lifecycle assurance, and traceable sourcing.

Supply support for PCA9541D/03,112 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 company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9541D/03,112 belongs to NXP's I²C-bus infrastructure portfolio, engineered specifically for high-availability systems requiring hardware-enforced master redundancy and deterministic bus recovery without slave-side reset dependencies.

FAQ

What is the power-up behavior difference between PCA9541D/03,112 and PCA9541D/01?

The PCA9541D/03,112 powers up with no channel selected - both upstream masters remain disconnected until explicit I²C command initiates control. In contrast, PCA9541D/01 powers up with Channel 0 (Master 0) automatically selected. This makes PCA9541D/03,112 ideal for symmetric dual-master systems where neither controller has inherent priority at boot, avoiding unintended bus occupation during cold start.

How does the PCA9541D/03,112 handle I²C bus recovery when switching masters during active communication?

When the PCA9541D/03,112 detects non-idle downstream traffic during a channel switch and bus initialization is disabled, it asserts the BUSOK interrupt to notify the new master that external recovery is required. If bus initialization is enabled (BUSINIT = 1), the PCA9541D/03,112 autonomously executes a 9-clock pulse sequence followed by NACK and STOP on SCL_SLAVE/SDA_SLAVE before connecting the new master - ensuring all slaves enter a known state without relying on their reset pins.

Can the PCA9541D/03,112 translate voltage levels between 1.8 V and 5 V I²C buses?

Yes. The PCA9541D/03,112 uses its VDD supply voltage to limit the maximum high-level voltage passed through its pass-gate switches. When powered at 3.3 V, it safely interfaces 1.8 V masters with 5 V slaves by clamping output high levels to ~3.3 V, eliminating need for discrete level shifters. All I/O pins are 6.0 V tolerant, supporting robust mixed-voltage operation across 1.8 V, 2.5 V, 3.3 V, and 5 V domains.

What is the function of the INT_IN pin on the PCA9541D/03,112?

The INT_IN pin on the PCA9541D/03,112 is an active LOW interrupt input that collects asynchronous interrupt signals from downstream I²C slaves (e.g., temperature sensors or power monitors). When enabled via the INTINMSK bit, it propagates those events to both upstream masters via their respective INT0 and INT1 outputs - enabling centralized fault response without requiring each master to poll slave status registers.

Does the PCA9541D/03,112 require external pull-up resistors on all I²C lines?

Yes. The PCA9541D/03,112 has no internal pull-up resistors on any I²C line - including SCL_MST0, SDA_MST0, SCL_MST1, SDA_MST1, SCL_SLAVE, SDA_SLAVE, INT0, INT1, and INT_IN. External pull-up resistors must be placed on each line, sized according to bus capacitance and target speed (e.g., 2.2 kΩ for 400 kHz operation with ≤400 pF load), and connected to the appropriate domain voltage (VDD or other rail).