What the PCA9545APW,118 does on the bus
The NXP PCA9545APW,118 is a 4-channel I²C switch in a 20-TSSOP package. It lets one upstream I²C master talk to any of four downstream bus segments, one at a time — useful for resolving address conflicts when multiple identical I²C slaves share the same bus, or for isolating bus segments during fault recovery.
The 2.3V–5.5V supply covers the common I²C bus voltages. At 3.3V the switch passes logic-low thresholds cleanly; at 5V it meets the full I²C specification for rise times and noise margins. No separate VDDIO pin — the same rail powers the internal logic and the bus switches, so the upstream and downstream segments must share the same supply voltage.
The 20-TSSOP body is 4.40 mm wide, 6.5 mm long, with 0.65 mm pin pitch — a standard footprint that routes easily on two-layer boards. Surface-mount only; no through-hole variant. The reel (Tape & Reel) and cut-tape options let you order exactly the quantity needed for prototype or production.
Store the reels dry: MSL level is not stated here, but 20-TSSOP packages typically run MSL 1 or 2 — check the reel label for floor-life limits before reflow.