16 I/O over two wires — the I²C port expander for tight pin budgets
The POR (power-on reset) feature ensures the outputs initialize to a known state — no floating pins at power-up that could drive loads unintentionally. This is the part to reach for when the MCU has run out of pins but you need to drive LEDs, read switches, or control a bank of relays on a remote board.
Each I/O can source 10 mA or sink 25 mA. That's enough to drive a standard LED directly through a current-limiting resistor — no external transistor needed for indicator lights. The 400 kHz clock keeps bus transactions short — reading all 16 inputs takes about 40 µs at that rate, which is fast enough for polling switch matrices or monitoring fault flags in a motor drive.
Package and footprint — 24-VFQFN with exposed pad
The device comes in a 24-VFQFN with exposed pad, measuring 4 mm × 4 mm. That's a small footprint for sixteen extra I/O — about the same board area as a 24-pin SOIC but with better thermal dissipation through the pad.