Why tantalum capacitors are derated (I)

Suitable conditions for the use of tantalum capacitors are -55 to +125 degrees, and a rated voltage can be applied within 85 degrees for testing. In other words, such conditions have shown that the temperature characteristics of tantalum capacitors are good, but one thing that is often overlooked is that testing under this condition is performed with a protective resistance of 1000 ohms. When the product is powered on, the voltage and current in the circuit have a very small change in the surge. Excessive transient current is suppressed by the series resistance, so the change will impact the tantalum capacitor.

In practical use, tantalum capacitors are often used in the power circuit without any resistor protection for filtering or charging and discharging. If such an circuit is used with an external power supply, the circuit will produce very high voltage at the moment of switching. Surge voltage and current change, therefore, in the use of such circuits, the tantalum capacitor will withstand more than the rated voltage at the instant of the switch and the large current impact and breakdown failure. Therefore, the use of tantalum capacitors in such circuits After a lot of experiments, it has been proved that if you want to ensure its sufficient reliability, you must use a large amount of depreciation to ensure that the sum of the surge voltage and reverse voltage added to the product instantaneously cannot exceed the rated value. Tantalum capacitors used in such low-impedance circuits are therefore required to be derated to 1/3 of the nominal value to ensure reliability.