The TAJD687K004SNJ: This is a 680 µF molded tantalum capacitor rated at 4 V DC, ±10% tolerance, in the D case size (2917 / 7343 metric). It is a surface-mount part from the TAJ series, designed for general-purpose bulk capacitance on low-voltage supply rails — think 3.3 V, 2.5 V, or 1.8 V power distribution where the 4 V rating gives headroom above the rail. The 500 mOhm ESR (at 100 kHz) matters for ripple current handling in a switching regulator output — higher ESR means more self-heating and ripple voltage at the load.
Rated lifetime is 2000 hours at the maximum operating temperature of 125°C. That is the accelerated-life test condition — in a 85°C ambient the actual service life is significantly longer, following the Arrhenius model. The 2000-hour figure at 125°C means the capacitor is designed for applications where the ambient temperature peaks near the upper limit — a power supply near a hot processor, a base-station power module, or an outdoor telecom enclosure. If your design runs continuously at 105°C, expect the lifetime to roughly double for every 10°C drop below 125°C.
Supplied by KYOCERA AVX.