NXP Semiconductors PCA9549BS,118

Overview

The PCA9549BS,118 from NXP Semiconductors is an octal I²C-bus-controlled analog bus switch providing eight independent bidirectional A↔B channels with 5 Ω typical ON-state resistance, 2.3 V to 5.5 V supply operation, and support for up to 400 kHz I²C clock frequency. It enables selective isolation of I²C sub-buses in multi-master or multi-peripheral systems such as server management controllers and modular sensor hubs.

For engineers reviewing the PCA9549BS,118 datasheet, PCA9549BS,118 pinout, PCA9549BS,118 application, or PCA9549BS,118 equivalent, key selection criteria include its HVQFN24 thermal-enhanced package, active-low RESET recovery function, individual channel enable via I²C control register, 5 V-tolerant inputs, and compatibility with SMBus timing requirements.

Technical Context

The PCA9549BS,118 implements a CBT (Cross Bar Technology) analog switch architecture controlled by an 8-bit I²C-accessible control register, where each bit independently enables or disables one of eight A↔B signal paths. Its internal state machine resets on power-up or active-low RESET assertion, initializing all channels to high-impedance open state.

It supports hot insertion and voltage translation between buses operating at different logic levels (e.g., 5 V main bus to 3.3 V or 2.7 V downstream segments), enabled by Vo(sw) ≤ 2.7 V when VDD ≤ 3.3 V - verified across 2.3–5.5 V supply range with specified Ron and leakage performance per JEDEC JESD78 latch-up and JESD22 ESD standards.

Key Specifications

Pinout & Package

HVQFN24 (SOT616-1) package: 4 mm × 4 mm × 0.85 mm body, no leads, 24-terminal thermal-enhanced quad flat layout with exposed center pad soldered to PCB ground for improved thermal and electrical performance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9548A and PCA9544A, the PCA9549BS,118 uniquely combines full 8-channel control, integrated active-low RESET, and lowest Ron in HVQFN24 - delivering superior fault resilience and signal fidelity for high-reliability embedded I²C architectures.

Availability

The PCA9549BS,118 is available at Aetrix Electronics and suitable for server baseboard management, modular sensor hubs, industrial PLC backplanes, and telecom line cards requiring stable component supply and long-term lifecycle assurance.

Supply support for PCA9549BS,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 company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and IoT applications.

The PCA9549 product line delivers I²C-bus multiplexing ICs designed specifically for reliable, low-latency isolation of I²C sub-buses in complex embedded systems with mixed-voltage domains and stringent fault-recovery requirements.

FAQ

What is the primary function of the PCA9549BS,118 in an I²C system?

The PCA9549BS,118 functions as an octal bidirectional analog bus switch that selectively connects or isolates eight independent I²C signal pairs (A↔B) under I²C control. It enables dynamic segmentation of a single I²C bus into multiple isolated sub-buses, preventing address conflicts and improving system reliability. The PCA9549BS,118 achieves this with low 5 Ω ON-resistance and supports voltage translation between mixed-voltage domains.

Does the PCA9549BS,118 support hot insertion and removal of I²C peripherals?

Yes, the PCA9549BS,118 supports hot insertion due to its no-glitch power-up behavior, latch-up immunity per JESD78 (>100 mA), and ability to isolate faulty segments without disrupting the main bus. Its active-low RESET pin allows immediate recovery from bus lock-up during live operation. The PCA9549BS,118 maintains high-impedance isolation on unselected channels, making it suitable for hot-swap I²C peripheral modules in telecom and industrial systems.

How does the PCA9549BS,118 handle voltage level translation between I²C domains?

The PCA9549BS,118 enables voltage translation by controlling Vo(sw) - the maximum output voltage seen at the B-side when the switch is ON. At VDD = 3.3 V, Vo(sw) is ≤ 2.7 V, allowing safe interfacing between a 5 V I²C master and 3.3 V or 2.7 V slaves. This eliminates external level shifters. The PCA9549BS,118 achieves this through its CBT switch architecture and is validated across 2.3–5.5 V supply range with specified leakage and Ron performance.

What is the role of the RESET pin on the PCA9549BS,118 and how must it be connected?

The RESET pin on the PCA9549BS,118 is an active-low asynchronous input that forces all eight channels into high-impedance open state and resets the I²C state machine, recovering from bus lock-up. It must be pulled HIGH via an external resistor to VDD and asserted LOW for ≥4 ns to trigger reset. The PCA9549BS,118 also includes internal power-on reset, ensuring all channels default to open at startup even if RESET is unconnected.

Can the PCA9549BS,118 be used with standard SMBus timing requirements?

Yes, the PCA9549BS,118 is explicitly designed for SMBus compatibility, supporting Fast-mode I²C up to 400 kHz with validated timing parameters including tHD;DAT (0.9 µs min), tSU;DAT (100 ns min), and tBUF (1.3 µs min). Its input filters suppress spikes ≤50 ns, and it meets SMBus electrical specifications including 5 V-tolerant inputs and defined VOL/VOH thresholds. The PCA9549BS,118 operates reliably across the full −40 °C to +85 °C industrial temperature range under SMBus conditions.