NXP Semiconductors PCA9540BD,112

Overview

PCA9540BD,112 from NXP Semiconductors is a 1-of-2 bidirectional I²C-bus translating multiplexer in SO8 package, enabling voltage-level translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses with 5 V-tolerant I/O pins, 400 kHz max clock frequency, and low 5–31 Ω ON-state resistance. It serves as a channel-selectable bus isolation and level-shifting interface in multi-voltage system management.

For engineers reviewing the PCA9540BD,112 datasheet, PCA9540BD,112 pinout, PCA9540BD,112 application, or PCA9540BD,112 equivalent, key selection criteria include its I²C-controlled channel switching, power-on reset behavior, VDD-dependent voltage clamping capability, standby current of ≤1 µA, and compatibility with SMBus standards in industrial and embedded control systems.

Technical Context

The PCA9540BD,112 implements a dual-channel pass-gate architecture controlled by an 8-bit I²C-accessible register where only bits B2–B0 determine channel selection (000 = no channel, 100 = channel 0, 101 = channel 1). Its internal power-on reset initializes all registers to zero and holds the I²C state machine inactive until VDD exceeds VPOR (1.6–2.1 V), ensuring glitch-free startup.

Voltage translation is achieved via VDD-referenced pass transistors: Vo(sw) is clamped to ≤2.8 V at VDD = 3.0–3.6 V, enabling safe interconnection of downstream 2.7 V/3.3 V peripherals with upstream 5 V masters. All I/O pins tolerate up to 7 V, and hot insertion is supported without bus contention.

Key Specifications

Pinout & Package

PCA9540BD,112 is housed in an SO8 plastic small outline package (SOT96-1), 8-pin, 3.9 mm body width, with gull-wing leads and standard surface-mount footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9544APWR and PCA9542AD,118, the PCA9540BD,112 offers optimal channel count and lowest standby current for dual-bus isolation tasks, while avoiding unnecessary complexity of 4-channel control or added reset pin routing - ideal for space-constrained, cost-sensitive industrial and medical designs requiring exactly two voltage-domain interfaces.

Availability

PCA9540BD,112 is available at Aetrix Electronics and suitable for server baseboard management, industrial PLC I/O expansion, and automotive body control modules requiring stable component supply, long-term industrial temperature support, and guaranteed I²C voltage translation performance.

Supply support for PCA9540BD,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 specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with leadership in I²C, SMBus, and power management ICs.

The PCA9540B family was designed specifically for robust, low-power I²C bus expansion and voltage-domain bridging in resource-constrained embedded systems - emphasizing reliability, interoperability, and ease of integration without external components.

FAQ

What is the maximum I²C clock frequency supported by the PCA9540BD,112?

The PCA9540BD,112 supports I²C clock frequencies up to 400 kHz, compliant with fast-mode I²C specifications. This allows full-speed communication with most modern I²C peripherals while maintaining signal integrity through its low 5–31 Ω ON-state resistance and ≤8 pF input capacitance. The PCA9540BD,112 achieves this performance across its full 2.3 V to 5.5 V supply range without derating.

Does the PCA9540BD,112 require external pull-up resistors on its downstream I²C channels?

Yes, the PCA9540BD,112 requires external pull-up resistors on each downstream SCx/SDx pair to establish the correct logic-high voltage level for that bus segment. Pull-up values must be selected based on the target downstream voltage (e.g., 3.3 V or 5 V) and bus capacitance, as the PCA9540BD,112 itself does not provide active pull-up. The PCA9540BD,112's 5 V-tolerant I/O pins ensure compatibility regardless of pull-up voltage.

How does the PCA9540BD,112 handle power-on initialization?

The PCA9540BD,112 incorporates an internal power-on reset (POR) circuit that holds the device in reset until VDD reaches VPOR (1.6–2.1 V), then initializes the control register to 00000000, deselecting all channels. This guarantees no downstream bus is inadvertently enabled at startup, preventing false START conditions or contention. The PCA9540BD,112 remains in this safe default state until the first valid I²C write command is received.

Can the PCA9540BD,112 translate between 1.8 V and 5 V I²C buses?

Yes, the PCA9540BD,112 supports voltage translation between 1.8 V and 5 V I²C buses by configuring VDD to match the lower of the two domains (e.g., 1.8 V or 2.5 V), which sets Vo(sw) to clamp downstream outputs accordingly. Its pass-gate architecture and 5 V-tolerant inputs allow the upstream side to operate at 5 V while downstream devices see only the VDD-limited voltage. The PCA9540BD,112 achieves this without external components or direction-control signals.

Is the PCA9540BD,112 pin-compatible with other members of the PCA9540B family?

Yes, the PCA9540BD,112 (SO8) shares identical pinout and function with PCA9540BDP (TSSOP8) and PCA9540BGD (XSON8) variants - all use the same SCL/SDA/VDD/SD0/SC0/VSS/SD1/SC1 ordering. This enables drop-in replacement across packages for layout flexibility, provided thermal and mechanical constraints are met. The PCA9540BD,112 maintains full functional equivalence across all three package types.