16-bit I²C GPIO expander in 24-TSSOP
The NXP PCA9535PW,112 is a 16-bit general-purpose parallel I/O expander controlled via the I²C bus or SMBus, clocked at 400 kHz. It adds 16 push-pull I/O lines to any host microcontroller that supports the two-wire interface, without consuming additional GPIO pins on the processor. Each I/O can source 10 mA or sink 25 mA, enough to drive LEDs, small relays, or level-shift discrete signals directly.
Package, temperature grade, and compliance
The part carries a power-on reset (POR) feature that initializes the I/O ports to a known state on power-up, preventing glitches on outputs before the host configures the registers. It also provides an interrupt output pin that signals the host when an input state changes, reducing polling overhead. ROHS3 compliant per.
Supply voltage and I/O drive capability
The 10 mA source / 25 mA sink per pin is sufficient for direct LED drive or interfacing with optocouplers without external buffers. Because the I/O are push-pull, they do not require external pull-up resistors for output mode — only the I²C bus lines (SCL, SDA) need pull-ups, which are typically already present on the bus. This simplifies the BOM and reduces board area.