NXP Semiconductors PCA9518D,112

Overview

The PCA9518D,112 from NXP Semiconductors is a 5-channel bidirectional I²C-bus and SMBus repeater hub designed to extend bus segments beyond the 400 pF capacitance limit. It operates from 3.0 V to 3.6 V, supports 0–400 kHz clock rates, features five independent SDA/SCL ports with active-HIGH enable inputs (EN1–EN4), and provides 5 V-tolerant I²C and enable pins for mixed-voltage system interfacing in industrial control backplanes.

For engineers reviewing the PCA9518D,112 datasheet, PCA9518D,112 pinout, PCA9518D,112 application, or PCA9518D,112 equivalent, this device enables scalable multi-segment I²C expansion with lock-up-free arbitration, clock stretching support across repeaters, and high-impedance I/O during partial power-down - critical for fault-tolerant sensor networks and modular embedded subsystems.

Technical Context

The PCA9518D,112 implements a BiCMOS 5-port hub architecture with open-drain SDA/SCL buffers per channel and four dedicated expansion pins (EXPSCL1/2, EXPSDA1/2) enabling cluster formation without direction control. Its dual-threshold input logic (VIL = 0.3VCC, VILc = 0.4 V) prevents inter-repeater lock-up by propagating "buffered LOW" signals at ~0.5 V output level while recognizing standard LOWs down to 70 mV below that threshold.

Each port supports Standard-mode (≤100 kHz) and Fast-mode (≤400 kHz) I²C devices, maintains full arbitration transparency, and isolates bus segments with only one repeater delay. The EN1–EN4 pins feature internal pull-ups and require idle-state transitions to avoid glitches; Port 0 (SCL0/SDA0) is always enabled and must be externally pulled up.

Key Specifications

Pinout & Package

PCA9518D,112 is packaged in SO20 (SOT163-1), a plastic small outline package with 20 leads and 7.5 mm body width. Pin functions are electrically identical to the TSSOP20 variant but differ in mechanical layout and thermal characteristics.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9517DGKR and PCA9515AD,118, the PCA9518D,112 uniquely supports expandable 5-port clustering, individual port enables (EN1–EN4), and 5 V-tolerant I/O - making it the only option for scalable, mixed-voltage, multi-master I²C architectures requiring >2 segments.

Availability

PCA9518D,112 is available at Aetrix Electronics and suitable for industrial sensor backplanes, modular PLC I/O expansion, automotive body control units, and medical device subsystem interconnects requiring stable component supply across long production lifecycles.

Supply support for PCA9518D,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 leader specializing in secure connectivity solutions for automotive, industrial, and IoT applications, with deep expertise in interface, power management, and embedded processing technologies.

The PCA9518D,112 belongs to NXP's I²C-bus repeater and hub product line, engineered specifically to solve bus capacitance limitations and mixed-voltage interoperability challenges in complex embedded systems with distributed slave topologies.

FAQ

What is the maximum supported I²C clock frequency for the PCA9518D,112?

The PCA9518D,112 supports I²C clock frequencies from 0 Hz up to 400 kHz, fully compliant with Fast-mode I²C specifications. While the device itself operates within this range, actual system frequency may be limited by cumulative propagation delay and RC time constants of external pull-up networks - design validation at 400 kHz requires verifying tPLH/tPHL margins against target bus timing budgets.

Does the PCA9518D,112 require external pull-up resistors on all I²C bus lines?

Yes, the PCA9518D,112 requires external pull-up resistors on every SDA and SCL line - both sides of each repeater channel - as it uses open-drain outputs. Port 0 (SCL0/SDA0) must always be pulled up since it has no enable pin. Pull-ups are also mandatory on all EXPxxxn expansion pins, even in single-device configurations, to ensure proper cluster signaling.

Can the PCA9518D,112 be used in series with PCA9515 or PCA9516 devices?

No, the PCA9518D,112 cannot be placed in series with PCA9515 or PCA9516 devices. Their differing LOW-level voltage thresholds (PCA9518D,112 uses static offset logic; PCA9515/16 use shifting) cause recognition failure: a "buffered LOW" from PCA9518D,112 (~0.5 V) falls outside the valid LOW input range of PCA9515/16, preventing signal propagation and risking bus lock-up.

How does the PCA9518D,112 handle power-down conditions?

When VCC drops below 2.0 V, the PCA9518D,112 places all I²C-bus I/O pins (SCLn/SDAn) into a high-impedance state, preventing contention on powered-down or partially powered segments. This behavior is intrinsic to the BiCMOS design and requires no external control - ensuring safe hot-swap and brown-out resilience in multi-rail systems.

What is the purpose of the EXPSCL1, EXPSCL2, EXPSDA1, and EXPSDA2 pins on the PCA9518D,112?

These four expansion pins enable multi-device clustering: EXPSCL1/EXPSDA1 drive LOW when any local SCL/SDA falls below 0.3VCC; EXPSCL2/EXPSDA2 respond to thresholds at ≤0.4 V. Wired together across multiple PCA9518D,112 units, they coordinate synchronized LOW-level propagation - allowing arbitrary cluster sizes without direction pins or external arbitration logic.