4-bit I/O expansion with I²C bus
The PCA9570GMH is a 4-bit general-purpose I/O expander from NXP that connects to the host controller via an I²C or SMBus serial interface running at 100 kHz. Each of the four I/O pins is configured as a push-pull output, so no external pull-up resistors are needed for the output side — the pin drives high or low directly. The POR (Power-On Reset) feature ensures the outputs power up in a known state — the I/O pins default to high-impedance until the host writes the configuration register. This avoids unintended glitches on the load during system power-up, which matters when the expander drives enable pins or relay coils that could trigger a false start.
Package and board-fit for space-constrained designs
The device is housed in an 8-lead XFQFN package with an exposed pad (8-XQFN, 1.6 x 1.6 mm body). The 4 mA source/sink current per I/O is enough to drive a logic-level load or a small LED directly, but not a relay coil without a buffer transistor.
Active production and compliance status
The part is ROHS3 compliant — no restricted substances above the threshold limits.