What this I²C GPIO expander brings to the board
The Maxim Integrated MAX7318AUG+T is a 16-bit I²C- and SMBus-compatible GPIO expander in a 24-TSSOP package. It provides 16 push-pull I/O ports that can be configured as inputs or outputs, with a built-in power-on reset (POR) that forces all ports to a known state at startup. The part operates across a 2V to 5.5V supply range, making it suitable for both 3.3V and 5V logic systems, and is rated for the full -40°C to 125°C industrial temperature range.
Supply voltage and logic-level compatibility
The 2V to 5.5V supply range means this expander can sit on a 3.3V or 5V rail without a level shifter on the I²C bus, as long as the bus voltage matches the VCC. The push-pull outputs source 31 mA and sink 43 mA per pin, enough to drive LEDs directly or pull relay coils through a transistor — just watch the total package dissipation when loading many outputs simultaneously.
The 24-TSSOP footprint is compact but hand-solderable with a fine tip; the 0.65 mm pitch calls for a steady hand or a reflow profile.
Clock speed and bus timing
The I²C interface runs at 400 kHz (fast mode), which is the standard ceiling for most microcontroller I²C peripherals. At this speed, a 16-bit read or write takes roughly 50 µs — fast enough for polling buttons, toggling LEDs, or reading DIP switches, but not for high-speed data streaming. The interrupt output (INT) lets the host avoid polling, waking only when an input changes.