EMC Question of the Week: July 30, 2018
Tantalum capacitors are often favored for low-to-medium frequency circuit board decoupling because, compared to ceramic capacitors, they have a
- lower inductance
- lower ESR
- higher reliability
- higher capacitance per volume
Answer
The best answer is “d.” Tantalum capacitors are a specific type of electrolytic capacitor that use tantalum metal for the anode. Their biggest advantage compared to ceramic capacitors is their much higher capacitance for a give package size. The large capacitance values help to provide decoupling at low-to-medium frequencies (e.g., less than about 10 MHz) where the impedance of the power bus decoupling is primarily determined by the amount of capacitance.
Multi-layer ceramic capacitors (MLCCs) have the advantage at frequencies where connection inductance is the primary factor limiting the capacitor’s ability to provide effective decoupling. MLCCs typically come in small packages with low connection inductance. They also have lower equivalent
series resistance (ESR).
Reliability can be an issue with both tantalum capacitors and MLCCs. However, in general, tantalums have no inherent reliability advantage that would cause them to be favored over MLCCs in decoupling applications.
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