2-channel I²C bus multiplexer in 14-TSSOP
The NXP PCA9543APW,118 is a 2-channel I²C multiplexer that lets a single I²C master talk to two independent downstream buses, each with its own address space and pull-up configuration.
Supply voltage — two operating windows
The PCA9543APW,118 operates from either a 2.3 V–3.6 V rail or a 4.5 V–5.5 V rail. If your I²C bus runs at 3.3 V, the lower window covers it; if you are on a 5 V bus, the upper window applies. There is no overlap between the two ranges, so pick the supply that matches your bus voltage — the part will not work at 4.0 V. This is a common gotcha when migrating a 5 V legacy design to 3.3 V: the part itself handles it, but the supply must land cleanly in one of the two bands.