28 I/Os on a 400 kHz I²C bus
The MAX7300ATL+T is a 28-pin I/O expander from Analog Devices that hangs off a single I²C bus at up to 400 kHz. Each of the 28 I/Os is configured as push-pull output or input, and the part generates an interrupt output on pin change — useful for a keypad matrix or sensor bank where the host MCU doesn't want to poll.
Each output can source 4.5 mA or sink 10 mA, enough to drive a standard LED directly or switch a small-signal relay through a transistor. For higher loads, the push-pull stage can be paralleled across multiple pins with firmware coordination.
Package and rework reality
Housed in a 40-TQFN with an exposed pad (6x6 mm body). The pad is the thermal and electrical ground — it needs a good solder joint to the board's ground plane.