What are the precautions for tantalum capacitor application

What are the precautions for tantalum capacitor application

The full name of tantalum capacitor is tantalum electrolytic capacitor, or tantalum capacitor, which belongs to one of electrolytic capacitors and uses metal tantalum as the medium. Tantalum capacitor was first developed by Bell Laboratories in 1956. It has excellent performance. It is a passive component with small volume and large capacitance in capacitors.

The selection of tantalum capacitors should mainly pay attention to the following aspects:

The reliability of tantalum capacitor will be affected by ambient temperature, such as temperature, humidity, mechanical stress, etc. sufficient margin shall be provided for the capacitor during use;

Try to keep the ripple current and ripple voltage at a small value;

The tantalum capacitor has polarity, and the reverse voltage cannot be applied during use. If the reverse voltage is unavoidable, the application time must be very short and not exceed the following value:

At 25 ℃, 10% of rated voltage or 1V, whichever is less

At 85 ℃, 5% of rated voltage or 0.5V, whichever is smaller;

At 125 ℃, 1% of rated voltage or 0.1V, whichever is smaller;

In order to ensure high reliability of tantalum capacitor, it is recommended that the voltage meet the following conditions:

For general applications, the use voltage is less than 70% of the rated voltage, and in low impedance circuits or power supply circuits, it is less than 30% of the rated voltage;

When used in circuits with temperature higher than 85 ℃ (not higher than 125 ℃), derating is required;

In order to avoid high-frequency transient interference, the parallel connection of ceramic capacitor and tantalum capacitor is often used in the line. Because ceramic capacitor has good high-frequency performance (up to 100 MHz), tantalum capacitor can generally only reach 100 kHz. After the combination of the two, high-frequency transient interference can be filtered by ceramic capacitor, and medium and low-frequency filtering is completed by tantalum capacitor.

In the MP3 backup power supply circuit, there is often kHz noise, which needs to be filtered by a larger capacitance. If aluminum electrolytic capacitor is selected, the volume of the whole PCB will be increased; Tantalum powder has a very high specific capacitance, and even a high capacitance value of 100uF can be maintained at a conventional shell number of B.