PCA9518PWT
PCA9518PWT - 5-Channel 400kHz I2C Hub | Texas Instruments
Texas Instruments PCA9518PWT is a five-channel bidirectional I2C/SMBus buffer and hub operating from 3 V to 3.6 V, supporting buses up to 400 kHz. The device is packaged in a 20-pin TSSOP (PW) and is designed to divide an I2C bus into buffered groups, each supporting up to 400 pF of bus capacitance. Its five downstream channels can expand a single controller interface into multiple isolated I2C branches for larger or more distributed systems.
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.
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