DS28E18 Communications Bridge

Analog Devices' DS28E18 enables both power and communications on a single wire, using a 1-wire protocol to link with I²C or SPI peripheral devices over 100 meters with only two wires. The solution eliminates up to five extender and switch ICs, significantly reducing connection costs and software complexity. In addition, only one programmable I/O port from the host microcontroller is necessary to operate a network with 10 to 20 nodes.

The IC provides a 512-byte command sequencer in SRAM that can be loaded with multiple I²C or SPI commands. Once loaded, the host controller sends a command to execute the sequence, power, and collect data from the attached I²C or SPI peripherals. A subsequent 1-wire command reads the collected data. Power for attached sensors or peripherals is sourced from the 1-wire line making the DS28E18 a very efficient solution to remotely power and control complex I²C or SPI devices such as sensors, ADCs, DACs, and display controllers.

When used as a bridge for I²C slave devices, the DS28E18 communicates at standard mode (100 kHz), fast mode (400 kHz) or fast-mode plus (Fm+, 1 MHz). In SPI mode, multiple clock rates up to 2.3 MHz are supported. Configuring for I²C or SPI operation is performed with a 1-wire command; I²C is the power-on default. When operating in I²C mode, two programmable GPIO pins are available for additional peripheral control.

Each DS28E18 provides a unique and secure 64-bit ROM identification number (ROM ID) that serves as the device's address on the 1-wire bus. Multiple DS28E18 devices can coexist with other devices in a 1-wire network and be accessed individually without affecting other devices.