NXP Semiconductors PCA9549D,118

Overview

PCA9549D,118 from NXP Semiconductors is an octal I²C-bus-controlled TTL-compatible bus switch IC used for dynamic I²C signal routing in multi-slave systems. It provides eight independent bidirectional A↔B channels with 5 Ω typical ON-state resistance, 2.3–5.5 V supply operation, and active-low RESET for bus fault recovery. It enables selective isolation of up to eight downstream I²C segments in server management, sensor hubs, and modular embedded systems.

For engineers reviewing the PCA9549D,118 datasheet, PCA9549D,118 pinout, PCA9549D,118 application, or PCA9549D,118 equivalent, key selection criteria include its 400 kHz Fast-mode I²C compatibility, 5 Ω Ron at 5 V, SO24 package footprint, 0.25 ns propagation delay, and hardware addressability via A0–A2 pins - all critical for low-latency, high-reliability I²C multiplexing in space-constrained industrial designs.

Technical Context

The PCA9549D,118 implements a CBT (Cross Bar Technology) architecture with eight independent pass-gate switches, each controlled by a dedicated bit in its 8-bit I²C-accessible control register. Its internal state machine interprets I²C write commands to open or close individual A↔B paths without affecting other channels.

It integrates hardware-level bus fault recovery via an active-low RESET input that forces all channels into high-impedance state and resets the I²C interface logic. The device supports hot insertion and operates across 2.3–5.5 V with 5 V-tolerant inputs, enabling voltage translation between mixed-voltage I²C domains (e.g., 5 V master ↔ 3.3 V/2.7 V slaves).

Key Specifications

Pinout & Package

PCA9549D,118 is supplied in SO24 (SOT137-1) plastic small outline package: 24-pin, 7.5 mm body width, 1.27 mm pitch, surface-mount. Pin 1 index located at top-left corner with notch or dot marking.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9548APWR and PCA9544ADW, the PCA9549D,118 uniquely combines full 5 V operation, integrated RESET for bus lockup recovery, and 5 Ω Ron - making it the only option among the three qualified for mixed-voltage, mission-critical I²C multiplexing where deterministic fault containment is mandatory.

Availability

PCA9549D,118 is available at Aetrix Electronics and suitable for server baseboard management, industrial sensor hubs, and modular test equipment requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for PCA9549D,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, and security ICs.

The PCA9549D,118 belongs to NXP's I²C-bus switch and multiplexer product line, designed specifically to solve signal routing, voltage translation, and bus isolation challenges in complex embedded systems with multiple I²C peripherals.

FAQ

What is the maximum I²C clock frequency supported by the PCA9549D,118?

The PCA9549D,118 supports I²C clock frequencies up to 400 kHz, meeting Fast-mode I²C specifications. Its 0.25 ns propagation delay and 5 Ω Ron ensure timing margins are maintained even at maximum speed, provided bus capacitance remains ≤400 pF per line as specified in the datasheet.

Does the PCA9549D,118 require external pull-up resistors on SCL and SDA lines?

Yes, the PCA9549D,118 requires external pull-up resistors on both SCL and SDA lines - consistent with standard I²C bus topology. The device itself does not integrate internal pull-ups, so resistor values must be selected based on bus capacitance, voltage, and desired rise time per I²C specification.

Can the PCA9549D,118 translate between different I²C voltage domains?

Yes, the PCA9549D,118 supports voltage translation: its 5 V-tolerant inputs allow connection to higher-voltage buses (e.g., 5 V), while operation from lower VDD (e.g., 3.3 V) sets Vo(sw) to clamp downstream signals - enabling reliable interfacing between 5 V masters and 3.3 V or 2.7 V slaves.

How does the RESET pin function on the PCA9549D,118?

The RESET pin on the PCA9549D,118 is active-low and asynchronously forces all eight switch channels into high-impedance state while resetting the I²C state machine. It must be pulled high via external resistor; asserting RESET low for ≥4 ns recovers from bus lockup conditions without power cycle.

Is the PCA9549D,118 pin-compatible with other members of the PCA954x family?

No, the PCA9549D,118 is not pin-compatible with PCA9544A or PCA9548A - though all share SO24 packaging, their pinouts differ significantly (e.g., PCA9544A includes INT pin; PCA9548A lacks RESET). The PCA9549D,118 pin configuration is unique to its octal-switch-with-RESET function.