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DS2408：1-Wire 8-Channel Addressable Switch

8-Channel, Bidirectional Port Expander can be Powered and Operated from a Single Communication Line

The DS2408 is an 8-channel, programmable I/O 1-Wire® chip. PIO outputs are configured as open-drain and provide an on resistance of 100Ω max. A robust PIO channel-access communication protocol ensures that PIO output-setting changes occur error-free. A data-valid strobe output can be used to latch PIO logic states into external circuitry such as a D/A converter (DAC) or microcontroller data bus. DS2408 operation is controlled over the single-conductor 1-Wire bus. Device communication follows the standard Dallas Semiconductor 1-Wire protocol. Each DS2408 has its own unalterable and unique 64-bit ROM registration number that is factory lasered into the chip. The registration number guarantees unique identification and is used to address the device in a multidrop 1-Wire net environment. Multiple DS2408 devices can reside on a common 1-Wire bus and can operate independently of each other. The DS2408 also supports 1-Wire conditional search capability based on PIO conditions or power-on-reset activity; the conditions to cause participation in the conditional search are programmable. The DS2408 has an optional VCC supply connection. When an external supply is absent, device power is supplied parasitically from the 1-Wire bus. When an external supply is present, PIO states are maintained in the absence of the 1-Wire bus power source. The RSTZ signal is configurable to serve as either a hard-wired reset for the PIO output or as a strobe for external circuitry to indicate that a PIO write or PIO read has completed.

Key Features Control Eight Independent I/O Port Pins from a Single Micro Port Pin Eight Channels of Programmable I/O with Open-Drain Outputs On-Resistance of PIO Pulldown Transistor 100Ω (max); Off-Resistance 10MΩ (typ) Individual Activity Latches Capture Asynchronous State Changes at PIO Inputs for Interrogation by the Bus Master Data-Strobe Output to Synchronize PIO Logic States to External Read/Write Circuitry Minimalist 1-Wire Interface Lowers Cost and Interface Complexity Built-in Multidrop Controller Ensures Compatibility with Other 1-Wire® Net Products Supports 1-Wire Conditional Search Command with Response Controlled by Programmable PIO Conditions Unique Factory-Lasered 64-Bit Registration Number Ensures Error-Free Device Selection and Absolute Part Identity Communicates to Host with a Single Digital Signal at 15.3kbps or 100kbps Wide Voltage and Temperature Operating Ranges Enables Robust System Performance 2.8V to 5.25V -40°C to +85°C Industrial Temperature Range

DS2408: Block Diagram Applications/Uses Industrial Control Instrumentation Test and Measurement Rack Based Systems Such as Central Office Switches, Wireless Base Stations, and PBXs

DataSheet

Parametrics

Quality and Environmental Data

• DS2408.pdf

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