NXP Semiconductors PCA9540BD,118

Overview

The PCA9540BD,118 from NXP Semiconductors is a 1-of-2 bidirectional I²C-bus translating multiplexer in SO8 package, enabling selective routing of SCL/SDA signals to one of two downstream SCx/SDx channels. It supports voltage translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses, features 5 V-tolerant I/O, operates from 2.3 V to 5.5 V supply, and delivers ≤31 Ω ON-state resistance at 3.6 V - used in multi-voltage sensor hub and PMIC communication systems.

For engineers reviewing the PCA9540BD,118 datasheet, PCA9540BD,118 pinout, PCA9540BD,118 application, or PCA9540BD,118 equivalent, key selection criteria include its I²C-bus channel isolation capability, VDD-dependent voltage clamping for level translation, power-on reset behavior with default deselected state, and compatibility with SMBus timing requirements up to 400 kHz.

Technical Context

The PCA9540BD,118 implements a single-pole double-throw (SPDT) analog switch architecture controlled via an 8-bit I²C slave register, where only bits B2–B0 determine channel selection (000 = no channel, 100 = channel 0, 101 = channel 1). Its pass-gate transistors use VDD as a gate-reference voltage to clamp output high-level voltage, enabling true bidirectional level translation without external logic.

Internal power-on reset initializes the control register to 0x00 (all channels deselected) and holds the I²C state machine inactive until VDD ≥ 1.6 V. The device requires no external pull-up resistors on upstream SCL/SDA but relies on downstream pull-ups set to target bus voltages - critical for mixed-voltage system partitioning in embedded controllers.

Key Specifications

Pinout & Package

PCA9540BD,118 uses the SO8 package (SOT96-1), 3.9 mm body width, 1.27 mm lead pitch, with gull-wing leads suitable for reflow soldering. Pin 1 is SCL, pin 2 is SDA, pin 3 is VDD, pin 4 is SD0, pin 5 is SC0, pin 6 is VSS, pin 7 is SD1, and pin 8 is SC1 - all pins are 5 V tolerant and support bidirectional signal flow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9544APWR and PCA9542AD,118, the PCA9540BD,118 provides optimal balance of low ON-resistance, proven voltage translation fidelity, and compact dual-channel routing - making it ideal for space-constrained, mixed-voltage I²C expansion where three or more channels are unnecessary.

Availability

PCA9540BD,118 is available at Aetrix Electronics and suitable for server baseboard management, industrial sensor hubs, and automotive body control modules requiring stable component supply and long-term industrial temperature support.

Supply support for PCA9540BD,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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in interface and power management ICs.

The PCA9540B family was designed specifically to solve I²C bus contention and voltage domain isolation challenges in resource-constrained embedded systems - delivering hardware-based channel selection and seamless level translation without firmware overhead.

FAQ

What is the maximum I²C clock frequency supported by the PCA9540BD,118?

The PCA9540BD,118 supports I²C clock frequencies up to 400 kHz, meeting Fast-mode I²C specifications. This is validated across its full operating voltage range (2.3 V to 5.5 V) and temperature range (−40 °C to +85 °C), with propagation delay ≤0.3 ns and timing margins preserved under 400 pF bus capacitance.

How does the PCA9540BD,118 perform voltage level translation between different I²C buses?

The PCA9540BD,118 uses its VDD supply voltage to set the maximum clamped output voltage (Vo(sw)) on downstream SCx/SDx lines. For example, setting VDD = 3.3 V limits Vo(sw) to ≤2.8 V, enabling safe communication between a 5 V master and 3.3 V or 2.5 V slaves - no external level shifters required.

Does the PCA9540BD,118 have a hardware reset pin?

No, the PCA9540BD,118 does not include a dedicated hardware reset pin. It relies solely on internal power-on reset (POR) that initializes the control register to 0x00 and deselects all channels upon VDD ramp-up. To force a reset, VDD must be lowered below 0.2 V for at least 5 µs.

Can the PCA9540BD,118 be used in hot-swap I²C applications?

Yes, the PCA9540BD,118 supports hot insertion due to 5 V-tolerant I/O pins, low standby current (≤1 µA), and glitch-free power-up behavior. Its internal POR ensures no channel is activated until the first valid I²C write, preventing bus contention during live insertion into an active I²C system.

What is the typical ON-state resistance of the PCA9540BD,118 and how does it affect I²C timing?

The PCA9540BD,118 exhibits a typical ON-state resistance of 5 Ω at VDD = 3.0–3.6 V. This low Ron minimizes RC delay on SDA/SCL lines, preserving rise/fall times and ensuring compliance with I²C timing budgets - especially critical at 400 kHz Fast-mode operation with up to 400 pF total bus capacitance.