PCA9518PWT - 5-Channel 400kHz I2C Hub | Texas Instruments
MPN： PCA9518PWT ✓ 啟用中PCA9518PWT 概覽
An I2C hub is a specialized interface IC that buffers the serial data and serial clock lines between an upstream controller and one or more downstream bus segments. Buffering reduces loading on the original bus and allows additional peripherals to be connected without exceeding the 400 pF capacitance limit associated with a conventional I2C segment. The PCA9518 operates in the broader hierarchy of I2C interface controllers, bus repeaters, bus hubs, interface ICs, and semiconductors.
The principal features of the PCA9518PWT include five downstream channels, bidirectional SDA and SCL buffering, a 3 V to 3.6 V supply range, and support for 400 kHz I2C operation. The buffered-channel architecture is useful when a board contains multiple sensor banks, EEPROMs, real-time clocks, display controllers, or power-management devices. Each downstream branch is isolated from the others, helping one oversized or heavily populated bus segment from degrading the entire system.
Texas Instruments describes the PCA9518 as an expandable five-channel bidirectional buffer for I2C and SMBus systems. Its architecture addresses the I2C protocol's maximum 400 pF bus-capacitance constraint by separating SDA and SCL into multiple groups. The buffered branches permit longer or more complex bus arrangements than a single unbuffered segment, provided each branch remains within its electrical and capacitive limits and follows the recommended connection and pull-up arrangement.
Typical uses include industrial sensor networks, multi-channel EEPROM access, data-acquisition modules, communication equipment, embedded control boards, and test systems requiring more I2C capacity than a single host bus can support. Because the hub is designed specifically for bidirectional I2C signaling, it can also support SMBus-style arrangements where the electrical and protocol requirements align. The operating-temperature grade shown for the PW package is -40 °C to 85 °C, making it suitable for commercial and industrial equipment.
When laying out a PCA9518PWT design, preserve short, clean SDA and SCL paths, place pull-up resistors at the locations specified by the manufacturer, and account for the capacitive loading of every downstream branch. Confirm that each branch stays within the 400 pF limit and verify timing margin at the intended 400 kHz operating rate. Avoid treating a buffered branch as a general-purpose isolated transceiver; it remains part of the connected I2C system.
This product page consolidates the manufacturer's bus-capacity constraints, operating limits, package information, and sourcing-oriented details into an engineering reference. It also distinguishes the genuine same-package family option from products that merely appear similar by function, helping designers assess footprint compatibility, I2C topology, temperature requirements, and replacement risk before committing a PCB design.
直接替換替代品，適用於 PCA9518PWT — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
此系列的變體
與下列產品可直接替換的同系列型號： PCA9518PWT （相同外形與佔位） — 差異在於 Package, Supply Voltage Range.
PCA9518PWT 規格
| Device Type | Five-channel bidirectional I2C/SMBus buffer and hub |
| Number of Downstream Channels | 5 channels |
| Supply Voltage Range | 3 V to 3.6 V |
| Maximum I2C Bus Speed | 400 kHz |
| Bus Capacitance per Buffered Group | 400 pF maximum |
| Protocol Support | I2C and SMBus |
| Data Line Type | Bidirectional SDA |
| Clock Line Type | Bidirectional SCL |
| 腳位數 | 20 pins |
| 封裝 | TSSOP (PW), 20 pins |
| 工作溫度範圍 | -40 °C to 85 °C |
| 安裝類型 | Surface mount |
| Ordering Option | PCA9518PWT tape-and-reel designation |
PCA9518PWT tssop (pw), 20 pins 腳位配置指南
PCA9518PWT（tssop (pw), 20 pins 封裝）的腳位配置。 腳位編號、功能與連接圖定義於製造商資料手冊中。請參閱該手冊以取得確切的封裝尺寸與焊接指引。
無詳細腳位定義資料： PCA9518PWT.
請參閱 資料表 以查看完整腳位配置。
典型應用
PCA9518PWT 適用於 6 應用s: Industrial Sensor Networks, Multi-Channel EEPROM Storage, Data Acquisition Systems, Communication Equipment, Embedded Control Boards, Test and Measurement Systems.
Industrial Sensor Networks
The PCA9518PWT fits industrial sensor networks where numerous remote I2C sensors would otherwise load one bus segment too heavily. Its five downstream channels create separate buffered groups for temperature, pressure, humidity, and digital-output sensors, each organized within the 400 pF capacitance constraint described by Texas Instruments. Operating from 3 V to 3.6 V supports common 3.3 V sensor ecosystems, while the -40 °C to 85 °C PW-grade range suits commercial and industrial equipment. Design each branch with short traces, appropriate pull-up placement, and a grounded return path to preserve 400 kHz timing margin.
推薦
Multi-Channel EEPROM Storage
The PCA9518PWT is useful in data-logging equipment that includes several I2C EEPROMs or other memory devices distributed across a board. Rather than connecting every device to a single high-capacitance segment, the hub divides them into five buffered SDA and SCL branches. This architecture can reduce the load seen by the controller and isolate each storage group within the 400 pF limit. The 3 V to 3.6 V operating range matches common 3.3 V memory devices, and the 400 kHz bus-rate limit should be checked against each memory's timing and system clock-stretching behavior.
推薦
Data Acquisition Systems
The PCA9518PWT supports modular data-acquisition systems that combine multiple analog front ends, digital converters, and sensor interfaces on one controller bus. Its five bidirectional branches allow converters to be assigned to separate circuit areas, reducing the capacitive and trace-length burden of one shared I2C network. A 3.3 V supply domain keeps the hub compatible with common mixed-signal equipment, while the 20-pin TSSOP package supports compact board layouts. Engineers should budget pull-up resistance for each branch, maintain a continuous ground reference, and verify acquisition timing because the maximum supported I2C rate is 400 kHz.
推薦
Communication Equipment
The PCA9518PWT can organize I2C management buses in communication equipment containing multiple line-card, management, status, and monitoring circuits. The five buffered groups prevent one densely populated section from determining the loading of the entire bus and permit short branch routing between functional blocks. Its 3 V to 3.6 V range aligns with typical 3.3 V logic, while the -40 °C to 85 °C grade supports equipment deployed across commercial and industrial environments. Place the hub near the branch distribution point, follow the manufacturer's pull-up guidance, and test worst-case timing when channels operate with different peripheral loads.
推薦
Embedded Control Boards
The PCA9518PWT is appropriate for embedded control boards that must connect a microcontroller to several remote I2C subsystems, such as display, touch, configuration, power, and expansion modules. Five downstream channels let the designer preserve useful branch segmentation even when no single peripheral group requires the full bus. The low-voltage 3 V to 3.6 V operating range enables direct integration into 3.3 V logic domains, and the compact 20-pin TSSOP is practical for space-conscious designs. Confirm that all devices on a branch use compatible logic levels and that each branch remains within the specified capacitance and timing limits.
推薦
Test and Measurement Systems
The PCA9518PWT helps organize I2C-connected instruments, programmable sources, and acquisition peripherals in a test system. Separate downstream branches can reduce loading on the host controller and shorten sensitive or heavily populated runs, while the 400 kHz rate supports moderately fast configuration and monitoring traffic. Its 3.3 V operating range enables use with common test-equipment logic, but operators should validate timing margin across the complete branch, including cable capacitance and slow peripheral transactions. Good grounding, disciplined pull-up selection, and separate routing for clock and data help prevent the hub from masking intermittent bus-edge problems.
推薦
推薦產品摘要
工程參考資料，適用於 PCA9518PWT — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | PCA9518PW |
|---|---|---|
| Package | TSSOP-20 (PW) | TSSOP-20 (PW) |
| Brand | Texas Instruments | Texas Instruments |
| Device Function | Five-channel bidirectional I2C/SMBus buffer and hub | Five-channel bidirectional I2C/SMBus buffer and hub |
| Number of Downstream Channels | 5 channels | 5 channels |
| Supply Voltage Range | 3 V to 3.6 V | 3 V to 3.6 V |
| Maximum I2C Bus Speed | 400 kHz | 400 kHz |
| Bus Capacitance per Buffered Group | 400 pF maximum | 400 pF maximum |
| Operating Temperature Range | -40 °C to 85 °C | -40 °C to 85 °C |
| Number of Pins | 20 pins | 20 pins |
| Protocol Support | I2C and SMBus | I2C and SMBus |
主要差異化特點
- Five-channel expansion architecture (對比PCA9518PW)
- Identical PCA9518 electrical function (對比PCA9518PW)
- Package continuity for existing PCB layouts (對比PCA9518DWT)
設計說明
Route each buffered SDA and SCL branch as a distinct pair, keeping the hub close to the branch distribution point. Avoid sharing narrow segments between downstream channels, and keep clock and data traces reasonably matched where branch lengths differ substantially. Calculate capacitance for every populated and unpopulated downstream branch; each group must remain within the manufacturer's 400 pF limit after accounting for devices, traces, connectors, and test points.
Do not assume that adding a hub permits unlimited cable length or peripheral count. A buffered branch still has capacitance, resistance, timing, and pull-up limitations, and an unpopulated branch can add unwanted loading through long traces. Review the official PCA9518 datasheet for enable, pull-up, unused-channel, and output-rise-time guidance. In particular, verify whether unused downstream pins must be left unconnected, terminated, or configured according to the device instructions.
Select pull-up resistors for the complete downstream bus segment rather than treating each hub channel as an isolated low-capacitance bus. Excessive pull-up resistance weakens rise time and reduces timing margin at 400 kHz, while excessive current can burden the hub or connected device. Use scope measurements at the slowest intended bus edge to confirm the SCL and SDA rise time, ringing, and voltage levels under the highest expected capacitive load.
合規資訊
The manufacturer product information confirms the function, voltage range, bus speed, package, pin count, and temperature range. Specific RoHS, REACH, AEC-Q100, lead-free, halogen-free, and conflict-minerals declarations require confirmation from the current manufacturer product documentation or a valid declaration.
