What the 300 mOhm ESR means for your rail
The TAJW227K002RNJ: This is a molded tantalum capacitor from the TAJ series, rated 220 µF at 2.5 V with a ±10% tolerance. At the full 125°C ambient limit, that self-heating eats into the derating margin, so the actual ripple current should be budgeted against the ESR and the thermal resistance of the board footprint.
The 2.5 V rating is common for 1.8 V and 2.5 V core rails — the derating rule of thumb (50% on voltage for tantalum) means this part should see no more than 1.25 V DC bias in a high-reliability design.