NXP Semiconductors PCA9540BDP/Q900J

Overview

PCA9540BDP/Q900J from NXP Semiconductors is a 1-of-2 bidirectional I²C-bus translating multiplexer in TSSOP8 package, enabling voltage-level translation between 1.8 V, 2.5 V, 3.3 V, and 5 V buses. It features 5 V-tolerant I/O, 0 Hz–400 kHz clock support, low Ron (≤11 Ω typical), and AEC-Q100 qualified operation up to +105 °C - used for isolating I²C segments in automotive body control modules.

For engineers reviewing the PCA9540BDP/Q900J datasheet, PCA9540BDP/Q900J pinout, PCA9540BDP/Q900J application, or PCA9540BDP/Q900J equivalent, key selection criteria include its channel-selectable architecture, VDD-controlled voltage clamping, hot-insertion capability, and guaranteed operation across −40 °C to +105 °C ambient range with standby current ≤1 µA.

Technical Context

The PCA9540BDP/Q900J implements a dual-channel pass-gate multiplexer controlled via an I²C-bus write to its 8-bit control register, where bits B2–B0 determine channel enable state and ensure no false bus transitions during switching. Its internal power-on reset initializes all channels deselected and places the I²C state machine in known idle mode.

Voltage translation is achieved by leveraging VDD as the clamp reference for downstream bus voltages: Vo(sw) is limited to ≤2.8 V at VDD = 3.6 V, enabling safe interfacing of 3.3 V peripherals with 5 V masters without external level shifters. All I/O pins are 5 V tolerant and support SMBus-compatible timing.

Key Specifications

Pinout & Package

TSSOP8 package (SOT505-1), 3 mm body width, 0.65 mm pitch, 8-lead plastic thin shrink small outline package.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9544APWR and PCA9542ADP, the PCA9540BDP/Q900J uniquely combines AEC-Q100 qualification, true bidirectional voltage translation across four voltage domains, and verified hot-insertion behavior - making it the sole option for automotive and mixed-voltage industrial I²C expansion where reliability and interoperability are non-negotiable.

Availability

PCA9540BDP/Q900J is available at Aetrix Electronics and suitable for automotive body control units, industrial sensor hubs, server baseboard management, and medical diagnostic equipment requiring stable component supply across extended temperature ranges.

Supply support for PCA9540BDP/Q900J 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 and power management ICs.

The PCA9540B family was designed specifically to solve I²C bus contention and voltage-domain mismatch in resource-constrained embedded systems - delivering scalable, pin-compatible multiplexing with integrated level translation and automotive-grade reliability.

FAQ

What is the maximum I²C clock frequency supported by the PCA9540BDP/Q900J?

The PCA9540BDP/Q900J supports I²C clock frequencies from 0 Hz up to 400 kHz, fully compliant with Fast-mode I²C specifications. This allows seamless integration into systems requiring higher-speed sensor or EEPROM communication without protocol modification. The device maintains timing integrity across its full operating temperature range (−40 °C to +105 °C), and its propagation delay is specified at ≤0.3 ns under typical load conditions.

Does the PCA9540BDP/Q900J require external pull-up resistors on downstream I²C channels?

Yes, the PCA9540BDP/Q900J requires external pull-up resistors on each downstream SCx/SDx pair. These resistors set the logic-high voltage level for their respective bus segments and must match the target downstream voltage domain (e.g., 1.8 V, 3.3 V, or 5 V). The upstream SCL/SDA lines also require pull-ups, typically referenced to the master's VDD. No internal pull-ups are provided.

How does the PCA9540BDP/Q900J achieve voltage level translation between different I²C buses?

The PCA9540BDP/Q900J uses its VDD supply voltage to clamp the maximum output voltage (Vo(sw)) on downstream SCx/SDx lines. When VDD is set to 3.3 V, Vo(sw) is limited to ≤2.8 V, allowing safe interfacing of 3.3 V peripherals with 5 V masters. This eliminates external level shifters. Translation direction is bidirectional and automatic - no configuration or direction control is needed.

Is the PCA9540BDP/Q900J pin-compatible with other members of the PCA9540B family?

Yes, the PCA9540BDP/Q900J shares identical pinout and footprint with all PCA9540B variants in TSSOP8 (SOT505-1), including PCA9540BDP and PCA9540BD. This enables direct substitution in existing designs. However, PCA9540BDP/Q900J is uniquely qualified to AEC-Q100 Grade 2 (−40 °C to +105 °C), whereas standard PCA9540BDP is rated only to +85 °C.

What happens to the downstream I²C channels during power-up of the PCA9540BDP/Q900J?

During power-up, the PCA9540BDP/Q900J asserts an internal Power-On Reset (POR) that holds all registers in default state (all zeroes) and deselects both downstream channels. This guarantees no unintended bus activity or false START/STOP conditions. Channels remain inactive until the first valid I²C write to the control register - ensuring glitch-free initialization critical in automotive and medical systems.