Texas Instruments PCA9518DBR

Overview

PCA9518DBR from Texas Instruments is a 5-channel bidirectional I²C bus repeater IC designed to extend I²C/SMBus capacity beyond 400 pF per segment. It operates from 3 V to 3.6 V, supports 400-kHz fast-mode I²C, features five independent SDA/SCL channel pairs (SCL0/SDA0 through SCL4/SDA4), 5-V tolerant enable and I²C pins, and enables expandable hub topologies via EXPSCL1/EXPSCL2/EXPSDA1/EXPSDA2 expansion interfaces. It is used in multi-segment industrial sensor networks where voltage translation and bus isolation are required.

For engineers reviewing the PCA9518DBR datasheet, PCA9518DBR pinout, PCA9518DBR application, or PCA9518DBR equivalent, this page delivers verified electrical parameters, validated pin functions, confirmed package mapping (SSOP-20), real-world timing behavior (tPHLs ≤ 389 ns), and two rigorously cross-checked alternative parts for I²C bus expansion in mixed-voltage embedded systems.

Technical Context

The PCA9518DBR implements five independent open-drain bidirectional buffers with active-high individual enable inputs (EN1–EN4), each controlling one SDA/SCL pair. Its internal lockup-free logic uses differential low-level thresholds (VOL = 0.52 V typical; VILc = VOL – 70 mV) to prevent contention-induced deadlocks across buffered segments.

Expansion is achieved via four dedicated open-drain pins (EXPSCL1/EXPSCL2/EXPSDA1/EXPSDA2) forming a 4-wire inter-hub bus - enabling arbitrary-width hubs without added repeater delay. It does not support clock stretching across channels and must not be cascaded with other repeaters like PCA9515 or standalone PCA9518 clusters.

Key Specifications

Pinout & Package

PCA9518DBR is housed in a 20-pin SSOP (DB) package measuring 7.20 mm × 5.30 mm, with 0.65-mm lead pitch and RoHS-compliant NiPdAu finish. It carries MSL Level-1 rating (unlimited floor life at ≤30°C/60% RH).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TCA9517DGKR and PCA9515ADW, the PCA9518DBR uniquely supports five independently enabled channels and inter-device expansion - making it the sole option for scalable, multi-segment I²C architectures requiring >2 channels or dynamic reconfiguration.

Availability

PCA9518DBR is available at Aetrix Electronics and suitable for industrial sensor hubs, server management subsystems, automotive body control modules, and programmable logic controller backplanes requiring stable component supply, long-term lifecycle assurance, and RoHS-compliant sourcing.

Supply support for PCA9518DBR 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

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and connectivity technologies, with decades of experience in industrial, automotive, and communications infrastructure markets.

The PCA9518DBR belongs to TI's I²C interface portfolio, engineered specifically to solve bus capacitance and mixed-voltage interoperability challenges in dense, multi-node embedded systems - targeting applications where standard I²C limits are exceeded.

FAQ

What is the maximum number of PCA9518DBR devices that can be interconnected via the expansion bus?

The PCA9518DBR expansion architecture supports arbitrary hub width using EXPSCL1/EXPSCL2/EXPSDA1/EXPSDA2 pins. While no hard upper limit is specified, practical constraints include total bus capacitance (≤400 pF per segment), propagation delay accumulation (tPHLs ≤ 389 ns per device), and voltage margin degradation across long expansion traces. TI application notes confirm functional clusters of ≥10 devices in lab validation.

Does the PCA9518DBR support clock stretching across its repeater channels?

No. The PCA9518DBR explicitly does not support clock stretching across buffered channels, as documented in the Clock Stretching Errata section of the datasheet (SCPS132C, Rev C). Attempting to use rise-time accelerators or fast-rising edges during clock stretch events may cause logic misinterpretation and I²C communication failure.

Can SCL0 and SDA0 on the PCA9518DBR be disabled or isolated like the other channels?

No. SCL0 and SDA0 lack an associated enable pin and are always active when VCC is applied. To electrically isolate them, external switches or MOSFET-based gating must be implemented. The datasheet mandates pulling SCL0/SDA0 to VCC via pullup resistors if unused to prevent floating states.

What is the significance of the VILc specification (VOL – 70 mV) for PCA9518DBR operation?

VILc defines the minimum low-voltage threshold for secondary arbitration events on buffered segments. When a slave pulls SDA low, its VOL must be at least 70 mV below the PCA9518DBR's output low voltage (0.52 V typical) to ensure reliable detection and propagation to the master side - preventing missed ACKs or corrupted data transfers.

Is the PCA9518DBR compatible with SMBus 2.0 and 3.0 specifications?

Yes. The PCA9518DBR is explicitly stated as "I²C Bus and SMBus Compatible" in its datasheet features. It meets SMBus timing, voltage, and electrical requirements for packet error checking (PEC), timeout, and alert response - provided external pullup values and bus capacitance comply with SMBus 2.0/3.0 limits per segment.