What the 16 I/O and 400 kHz bus mean for your design
The MAX7312AUG+T is a 16-bit I2C- and SMBus-compatible port expander from Analog Devices, designed to add GPIO to a microcontroller or processor that has run out of pins. The 16 I/O lines are configured as push-pull outputs, meaning each pin can source 31 mA or sink 43 mA — enough to drive an LED directly or switch a small relay without an external transistor. The I2C bus runs at 400 kHz, which is the standard fast-mode speed. For reading or writing 16 bits of data, the bus transaction takes roughly 50 µs, so the expander is well suited for status polling or setting outputs at a control-loop rate of a few kilohertz. The interrupt output lets the expander signal the host only when an input changes, avoiding constant polling and saving bus bandwidth.
Power-on reset and supply flexibility
The POR (power-on reset) feature ensures that all I/O pins default to a known high-impedance state at power-up, so external loads are not driven until the host configures the expander. This is critical in systems where an output could accidentally energize a load during startup. The wide range also allows the expander to run on a battery that droops below 3 V without needing a separate regulator.
The supplier device package is 24-TSSOP, and the part is available in Tape & Reel (TR) or Cut Tape (CT) for pick-and-place assembly.