The NXP PCAL6408ABSHP is an 8-bit general-purpose I/O expander that connects to a host controller via an I²C or SMBus interface running at up to 400 kHz. It provides eight configurable I/O pins that can be set as open-drain or push-pull outputs, with a per-pin source/sink capability of 10 mA source and 25 mA sink. A dedicated interrupt output signals the host when an input changes, reducing polling overhead. The wide supply range of 1.65 V to 5.5 V lets it bridge 1.8 V and 3.3 V logic domains on the same bus. The POR (Power-On Reset) feature ensures the outputs start in a known state after power-up, which matters for driving relays or LEDs that must not glitch.
Supply voltage and I2C compatibility
The 1.65 V minimum supply means the PCAL6408ABSHP works directly on a 1.8 V I²C bus without a level shifter — a common requirement in battery-powered IoT nodes and low-voltage SoC designs. At the 5.5 V maximum it also mates with legacy 5 V logic. The 400 kHz clock matches standard-mode I²C and SMBus; no speed downgrade needed.
The small footprint suits space-constrained boards in portable instruments or sensor modules.