NXP Semiconductors PCA9542AD,118

Overview

PCA9542AD,118 from NXP Semiconductors is a 1-of-2 bidirectional I²C-bus translating multiplexer with integrated interrupt logic, designed to isolate and route I²C traffic between one upstream master and two downstream slave channels. It supports voltage translation across 1.8 V, 2.5 V, 3.3 V, and 5 V domains, features active-low INT0/INT1 inputs and a wired-AND INT output, and operates from 2.3 V to 5.5 V supply. It is used in server management subsystems where multiple I²C peripherals share a single bus.

For engineers reviewing the PCA9542AD,118 datasheet, PCA9542AD,118 pinout, PCA9542AD,118 application, or PCA9542AD,118 equivalent, this device enables robust channel selection via I²C control register writes, hot-insertion support, glitch-free power-up, and precise interrupt source identification - critical for fault-tolerant embedded monitoring and modular system architectures.

Technical Context

The PCA9542AD,118 implements a dual-channel pass-gate multiplexer architecture controlled by an 8-bit I²C-accessible control register, where bits B2–B0 determine channel selection (000 = no channel, 100 = channel 0, 101 = channel 1). Its interrupt logic latches INT0/INT1 states into read-only bits 5–4 of the same register, enabling software-driven channel interrogation without requiring physical channel activation.

Voltage translation is achieved through VDD-referenced pass-gate threshold control: Vo(sw) is clamped to ≤2.8 V at VDD = 3.6 V, allowing safe interfacing between 3.3 V upstream and 2.7 V downstream buses. The device includes internal power-on reset that initializes all registers to zero and deselects both channels, ensuring deterministic startup behavior.

Key Specifications

Pinout & Package

PCA9542AD,118 is housed in a plastic small outline package (SO14) per SOT108-1 standard, with 14 leads and 3.9 mm body width. Thermal resistance is 127 °C/W (junction-to-ambient), suitable for convection-cooled industrial PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9542APWR and PCA9544APW, the PCA9542AD,118 delivers optimal balance of channel count, package compatibility, and interrupt-aware routing for compact, dual-peripheral I²C systems - especially where deterministic power-up state and low Ron are critical.

Availability

PCA9542AD,118 is available at Aetrix Electronics and suitable for server management, industrial sensor hubs, modular test equipment, and automotive diagnostic interfaces requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for PCA9542AD,118 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, power management, and embedded processing technologies.

The PCA9542A product line was developed to solve I²C bus contention and voltage-domain isolation challenges in dense, multi-peripheral embedded systems - delivering integrated multiplexing, interrupt aggregation, and level translation in a single SO14 package.

FAQ

What is the default state of the PCA9542AD,118 after power-on reset?

Upon power application, the PCA9542AD,118 enters a reset state until VDD reaches VPOR (1.6–2.1 V), then initializes all registers to zero and deselects both channels. This ensures no downstream I²C segment is inadvertently activated at startup, preventing bus conflicts and false ACKs. The PCA9542AD,118 remains in this safe, high-impedance state until the host writes a valid channel-enable value to the control register.

How does the PCA9542AD,118 handle voltage translation between different I²C bus domains?

The PCA9542AD,118 uses its VDD supply voltage to clamp the maximum pass-gate output voltage (Vo(sw)), enabling translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses. For example, setting VDD = 3.3 V limits Vo(sw) to ≤2.8 V, allowing safe interfacing of a 5 V upstream bus with 2.7 V downstream peripherals. External pull-up resistors on each SCx/SDx pair set final bus voltage levels, and all I/O pins are 5 V tolerant.

Can unused interrupt inputs (INT0 or INT1) be left floating on the PCA9542AD,118?

No - unused interrupt inputs on the PCA9542AD,118 must not be left floating. They must be tied to VDD via a pull-up resistor to ensure defined logic states and prevent noise-induced false interrupts. The datasheet explicitly states that floating interrupt inputs compromise reliability. This requirement applies regardless of whether the interrupt function is actively used in the design, and the PCA9542AD,118 will correctly report their status in the control register's INT0/INT1 bits.

What is the maximum I²C clock frequency supported by the PCA9542AD,118?

The PCA9542AD,118 supports I²C clock frequencies up to 400 kHz in Fast-mode, as confirmed by dynamic characterization in Table 10 of the datasheet. Propagation delay from SCL to SCx or SDA to SDx is specified at ≤0.3 ns, ensuring minimal timing impact on high-speed transactions. This makes the PCA9542AD,118 suitable for PMBus-compliant power supply monitoring and other latency-sensitive I²C applications.

Is the PCA9542AD,118 pin-compatible with the PCA9542APW variant?

No - the PCA9542AD,118 (SO14, SOT108-1) and PCA9542APW (TSSOP14, SOT402-1) share identical pin functions and ordering information but differ in physical package dimensions, lead pitch, and thermal resistance (127 °C/W vs. 175 °C/W). While schematic symbols and netlists can be reused, PCB footprints are not interchangeable. The PCA9542AD,118 requires the SO14 land pattern with 3.9 mm body width and 1.27 mm lead pitch.