What the DS2408S+ does on the bus
The Maxim Integrated DS2408S+ is an 8-channel programmable I/O expander that communicates over a single-wire data line plus ground — the 1-Wire interface. Each of the eight I/O pins is an open-drain output that can sink current or be read as a digital input. The part operates from a 2.8V to 5.25V supply, covering both 3.3V and 5V logic rails without external level shifters. It is housed in a 16-SOIC package (0.154" width, 3.90mm body) and rated for industrial temperature environments from -40°C to 85°C.
1-Wire interface — what it means for the BOM
The 1-Wire bus uses only one data wire plus ground, so the DS2408S+ adds eight digital I/O lines to a system that already has a 1-Wire master (typically a microcontroller with a 1-Wire port or a bit-banged GPIO). This saves board space and connector pins compared to an I²C or SPI expander. The open-drain outputs can sink current from external loads (LEDs, relays, optocouplers) when pulled low; the high-impedance state lets the line be read as an input. No interrupt output is provided, so the master must poll the device to detect state changes.
Lifecycle and sourcing reality
The part is ROHS3 compliant.