What the 4.7 µF / 16 V rating means on your rail
The TAJA475K016RNJ: This is a 4.7 µF tantalum capacitor rated for 16 V continuous — a common choice for bulk decoupling on 3.3 V, 5 V, or 12 V rails where the voltage derating (typically 50-80% of rated voltage) keeps the failure rate low. The 1206 case fits a standard footprint; the 4 Ω ESR sets the ripple-current ceiling, so if your rail carries more than a few hundred mA of ripple at 100 kHz, the self-heating will push the core above the 125 °C limit.
This is the same range as the TAJ series standard — expect it in outdoor telecom, engine-bay modules, and avionics power supplies where the board sees thermal cycling from cold soak to under-hood heat.