Texas Instruments PCA9518DWR

Overview

PCA9518DWR from Texas Instruments is a five-channel bidirectional I²C/SMBus buffer hub designed to extend bus capacitance beyond 400 pF by segmenting and buffering SDA/SCL lines. It operates from 3 V to 3.6 V, supports 400-kHz fast-mode I²C, features five independent active-high enable inputs (EN1–EN4), and provides 5-V tolerant I²C and enable pins for mixed-voltage system interfacing - used in multi-segment industrial sensor networks with isolated voltage domains.

For engineers reviewing the PCA9518DWR datasheet, PCA9518DWR pinout, PCA9518DWR application, or PCA9518DWR equivalent, key selection criteria include its expandable hub topology, lockup-free arbitration handling, individual channel enable control, 70-mV low-level contention margin (VOL – VILc), and SOIC-20 package compatibility with legacy 3.3-V/5-V I²C subsystems.

Technical Context

The PCA9518DWR implements five independent open-drain bidirectional buffers, each with dedicated SDA/SCL pairs (SCL0/SDA0 through SCL4/SDA4) and corresponding enable inputs (EN1–EN4). Its expansion interface uses four dedicated pins (EXPSCL1/2, EXPSDA1/2) to form a 4-wire inter-hub bus enabling cluster-based scaling without added repeater delay.

It employs asymmetric low-level voltage thresholds: internal VOL ≈ 0.52 V, while valid input low (VILc) is defined as ≥70 mV below VOL to prevent lockup during contention. The device includes internal power-on-reset (VPOR) and supports powered-off high-impedance I²C pins - critical for hot-swap and partial-power-down operation.

Key Specifications

Pinout & Package

PCA9518DWR is supplied in a 20-pin SOIC (DW) package measuring 12.80 mm × 7.50 mm, with standard gull-wing leads and RoHS-compliant NiPdAu finish. It is rated MSL Level-1 (unlimited floor life) and supports reflow up to 260°C peak.

Key Features

Applications

Equivalent & Alternatives

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

Compared with PCA9517ADW and TCA9517APWR, the PCA9518DWR uniquely delivers five independently controllable channels plus inter-hub expansion - making it the only option for scalable, multi-segment, mixed-voltage I²C architectures requiring >2 channels and cluster coordination.

Availability

PCA9518DWR is available at Aetrix Electronics and suitable for industrial sensor networks, modular server management, telecom power monitoring, and automotive body control systems requiring stable component supply and long-term production continuity.

Supply support for PCA9518DWR 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 over 50 years of innovation in industrial, automotive, and communications markets.

The PCA9518DWR belongs to TI's I²C interface and bus expansion product line, engineered specifically to solve I²C bus capacitance limitations and mixed-voltage interoperability challenges in dense, modular, and safety-critical embedded systems.

FAQ

What is the maximum I²C bus speed supported by the PCA9518DWR?

The PCA9518DWR supports 400-kHz fast-mode I²C operation. Its propagation delays (tPHLs up to 389 ns, tPLHs up to 265 ns) and edge-rate control circuits ensure timing compliance at this rate across all five channels. It does not support standard-mode (100 kHz) exclusively - the 400-kHz rating applies under recommended conditions (VCC = 3.0–3.6 V, TA = –40°C to 85°C). The PCA9518DWR is not rated for ultra-fast-mode (1 MHz) operation.

Does the PCA9518DWR support clock stretching across buffered segments?

No, the PCA9518DWR does not support clock stretching across repeater segments. The datasheet explicitly states this limitation and includes an errata section warning that rise-time accelerators must be avoided due to static offset and overshoot risks during stretching events. Clock stretching initiated by a slave on one segment will not propagate to the master side; the PCA9518DWR treats stretched clocks as invalid low pulses and may cause communication failure if stretching exceeds design margins.

Can the PCA9518DWR be used with a 5-V VCC supply?

No, the PCA9518DWR requires a VCC supply strictly between 3.0 V and 3.6 V. While its I²C and enable input pins are 5-V tolerant (VI up to 7 V), applying 5 V to the VCC pin exceeds the absolute maximum rating of 7 V but violates the recommended operating condition and will damage the device or cause functional failure. Always power VCC from a regulated 3.3-V source; 5-V signals may be safely applied only to SDA, SCL, EN, EXPSDA, and EXPSCL pins.

How does the PCA9518DWR prevent bus lockup during arbitration?

The PCA9518DWR prevents lockup using a dual-threshold low-level detection scheme: its output low voltage (VOL) is ~0.52 V, while the valid input low threshold for contention (VILc) is specified as at least 70 mV below VOL. This ensures that a driven low on one segment propagates as a slightly higher buffered low (~0.52 V) to other segments, which remains above the VILc of downstream receivers - avoiding false recognition and oscillatory behavior during arbitration release. This design is validated in the electrical characteristics table (VOL – VILc ≥ 70 mV).

What is the function of the EXPSCL1, EXPSCL2, EXPSDA1, and EXPSDA2 pins on the PCA9518DWR?

These four pins form a 4-wire open-drain expansion bus enabling communication between multiple PCA9518DWR devices in a cluster. EXPSCL1/2 indicate falling edges on local SCL lines (at 0.3×VCC and 0.4×VCC thresholds); EXPSDA1/2 do the same for SDA lines. When interconnected across hubs, they coordinate low-level propagation across the entire cluster with only one repeater delay - allowing scalable hub topologies (e.g., 10-, 15-, or 20-channel systems) without performance degradation. Pullup resistors are mandatory on all four lines, even for single-device use.