8 GPIOs on the I²C bus
The PCA9534ADB is an 8-bit I²C-bus and SMBus I/O expander from Texas Instruments. It adds eight general-purpose I/O pins to a system through a two-wire serial interface, freeing up processor GPIOs for other tasks.
Supply, temperature, and drive
Each I/O pin can source 10 mA or sink 25 mA — enough to drive an LED directly or switch a small-signal relay through a transistor. The push-pull output structure eliminates the need for external pull-up resistors on output pins. An open-drain interrupt output (INT) asserts when an input changes state, letting the host processor poll the expander only on demand rather than continuously. This reduces I²C bus traffic and saves CPU cycles in power-sensitive designs.
Package and board-fit
The supplier device package is 16-SSOP, and the device is shipped in a Tube. The 1.27 mm pin pitch of the SSOP package is layout-friendly for two-layer boards. Standard decoupling — a 0.1 µF ceramic near the VCC pin — is sufficient; the POR circuit handles the reset timing.