Capacitance, voltage, and package fit
The TAJS684M025RNJ: This is a 0.68 µF molded tantalum capacitor rated at 25 V, in a 1206 (3216 Metric) surface-mount package. The ±20% tolerance is standard for tantalum electrolytics; the actual capacitance at 25 °C and 0 V bias will be within 0.54 µF to 0.82 µF. The 10 Ohm ESR (Equivalent Series Resistance) is typical for a small-case tantalum at this capacitance and voltage. It limits ripple current handling — for a 25 V rail with 100 mV ripple, the capacitor can handle about 10 mA RMS before self-heating becomes a concern. If your circuit demands lower ESR, consider a polymer or higher-voltage tantalum in a larger case.
The molded case and 1206 footprint keep the thermal mass low — it tracks the board temperature closely.