1 µF, 16 V, 11 Ohm ESR — the decoupling and filtering fit
The TAJA105K016RNJ: At 1 µF and 16 V, this TAJ-series tantalum sits between a local bypass cap for a 12 V rail and a small bulk storage element for a 3.3 V or 5 V supply. The 11 Ohm ESR is the thermal ceiling — at ripple current the self-heating rises with the square of the current, so a 100 kHz switching regulator drawing 50 mA ripple will stay within the 125°C limit, but a higher-frequency buck with 200 mA ripple may push the internal temperature above the derating curve.
The 1206 case (3.20 mm x 1.60 mm) keeps the footprint small enough for dense PCB layouts, but the 1.80 mm seated height means it will not fit under a 2 mm board-to-board gap.
No official second-source or successor — the TAJ series is a standard molded tantalum, so a functionally equivalent part from Kemet or Vishay with the same case code, voltage, and capacitance will fit the same pad layout, but confirm the ESR and temperature rating match your derating budget.