The TAJB475K020KNJ is a 4.7 µF molded tantalum capacitor rated at 20 V with ±10 % tolerance. The 3 Ohm ESR at 100 kHz is the spec that determines how much ripple current the part can handle before self-heating exceeds the 125 °C limit — at 100 kHz, a 3 Ohm ESR limits ripple current to roughly 200 mA RMS for a 125 mW self-heating budget. For a 12 V rail decoupling application, the 20 V rating provides 33 % derating, which is the standard practice for tantalum capacitors to avoid surge failures.
Temperature range and life rating
The 2000-hour life rating at 125 °C is the accelerated test condition; every 10 °C drop in operating temperature roughly doubles the expected life, so at 85 °C the useful life extends well beyond 10,000 hours.