NXP Semiconductors PCA9518D,118

Overview

The PCA9518D,118 from NXP Semiconductors is a 5-channel bidirectional I²C-bus and SMBus repeater hub in SO20 package, operating from 3.0 V to 3.6 V supply, supporting up to 400 kHz clock frequency, with open-drain SDA/SCL I/O, active-HIGH individual enable inputs (EN1–EN4), and 5 V tolerant I²C-bus pins - used to extend I²C-bus segments while preserving arbitration, clock stretching, and multi-master capability in industrial control backplanes.

For engineers reviewing the PCA9518D,118 datasheet, PCA9518D,118 pinout, PCA9518D,118 application, or PCA9518D,118 equivalent, this device enables scalable bus segmentation with single-repeater-delay latency, voltage-level translation between 3.3 V and 5 V subsystems, and robust lock-up-free operation across distributed I²C domains - critical for high-reliability embedded systems requiring deterministic timing and fault-isolated bus expansion.

Technical Context

The PCA9518D,118 implements five independent bidirectional open-drain buffers with hysteresis-based input detection and static offset logic to prevent inter-repeater lock-up. Its expansion interface (EXPSCL1/2, EXPSDA1/2) uses differential threshold levels (e.g., 0.3VCC and 0.4VCC) to coordinate state propagation across clustered hubs without direction control pins.

Each channel features active-HIGH enable with internal pull-ups, and port 0 is permanently enabled with mandatory external pull-ups. The device supports Standard-mode (≤100 kHz) and Fast-mode (≤400 kHz) I²C-bus devices, maintains full arbitration transparency, and guarantees VOL−VILc ≥ 70 mV to ensure reliable contention detection during multi-master handshaking.

Key Specifications

Pinout & Package

PCA9518D,118 is housed in a plastic small outline package (SO20, SOT163-1) with 20 leads and 7.5 mm body width, optimized for automated PCB assembly and thermal performance in dense layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9517D,118 and TCA9517APWR, the PCA9518D,118 uniquely supports scalable multi-hub clusters via EXPxxxn pins and offers per-channel enable control - essential for dynamic bus reconfiguration and fault containment in large-scale embedded systems.

Availability

PCA9518D,118 is available at Aetrix Electronics and suitable for industrial backplane interconnect, multi-voltage sensor subsystems, and redundant server management buses requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for PCA9518D,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 bus technology.

The PCA9518D,118 belongs to NXP's I²C-bus repeater and hub product line, engineered specifically to solve bus capacitance limitations and voltage-domain interoperability in complex embedded systems.

FAQ

What is the maximum I²C-bus clock frequency supported by the PCA9518D,118?

The PCA9518D,118 supports I²C-bus clock frequencies up to 400 kHz, compliant with Fast-mode specification. System-level frequency may be lower depending on total propagation delay across segments, but the device itself imposes no inherent limitation below 400 kHz. PCA9518D,118 maintains full timing compliance including setup/hold windows and arbitration cycles at this rate.

Can the PCA9518D,118 be used to connect 3.3 V and 5 V I²C-bus segments?

Yes - the PCA9518D,118 features 5 V tolerant SDA, SCL, and enable pins, allowing direct interface with 5 V pull-up resistors while operating from a 3.3 V supply. This eliminates external level-shifting components. PCA9518D,118 preserves signal integrity and timing across voltage domains without protocol modification.

Does the PCA9518D,118 require external pull-up resistors on all I²C-bus lines?

Yes - external pull-up resistors are required on every SDA and SCL line (SCL0/SDA0 through SCL4/SDA4), including port 0 which has no enable pin and must always be pulled up. Pull-ups are also mandatory on all EXPxxxn expansion pins, even in single-device configurations. PCA9518D,118 does not integrate pull-ups.

How does the PCA9518D,118 prevent lock-up conditions in multi-repeater clusters?

The PCA9518D,118 uses dual-threshold expansion signaling: EXPSCL1/EXPSDA1 trigger at 0.3VCC, while EXPSCL2/EXPSDA2 trigger at 0.4VCC. This staggered detection avoids simultaneous drive conflicts between repeaters. PCA9518D,118 achieves lock-up-free operation without direction pins or centralized arbitration logic.

Is the PCA9518D,118 compatible with standard I²C-bus arbitration and clock stretching?

Yes - the PCA9518D,118 transparently passes arbitration pulses and clock stretch events between segments. Its open-drain buffers and VOL−VILc ≥ 70 mV margin ensure that contention-driven LOW states are correctly detected and propagated. PCA9518D,118 requires no firmware changes or timing adjustments to support multi-master systems.