Capacitance, voltage, and ESR — the three numbers that size the part
The TPSA475K020A1800 is a 4.7 µF molded tantalum capacitor rated at 20 V with a 1.8 Ohm ESR. For decoupling a 3.3 V rail, the 20 V rating provides over 5× derating, keeping the part well within its safe operating area even under transient overvoltage. The 1.8 Ohm ESR limits ripple current to roughly 0.5 A RMS at 85°C — enough for moderate switching-regulator output filtering but not for high-ripple bulk storage.
Temperature range and case size — where it fits on the board
The 1206 (3216 Metric) case measures 3.20 mm x 1.60 mm with a seated height of 1.80 mm — a standard footprint that mates with common pick-and-place nozzles and reflow profiles.