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Q:

What is the maximum voltage for MLCCs?

A:

Expected lifetime and failure rates are based on the component’s rated voltage. The rated voltage is usually lower than the “breakdown voltage”, which depends on the capacitor’s dielectric-typed and rated voltage.

Breakdown Voltage

Typically for MLCCs up to 200V, the breakdown voltage is 4x rated. While parts rated for 200V up to 1000V the breakdown voltage may be up to 1.2X rated. Parts over 1000V may have a breakdown such as 1.15X rated. (Please see a capacitor’s datasheet for specified values.)  These breakdown multipliers will decrease with increasing temperature.

Self-Heating

The breakdown voltage does not change over frequency. However, the impedance of a capacitor is lower with higher frequencies. This change in impedance may see a rise in ripple current. The current increase creates a self-heating,  dependent on the component’s ESR.

Calculating Power Loss

The power loss (PLoss) of the MLCC requires a reduction in voltage to keep the current below a limit the power limit of the capacitor.

Ripple Current and Voltage for 1210 MLCC 106 25V

Figure 1 – KEMET WebSPICE Example

Max RMS Voltage based on Z

Equation 1

For power calculation use the RMS (root mean square) values.

The VRMS = Vr/ √2 is only valid for sinusoidal waveforms. For other waveform shapes, use the integral shown in Equation 2.

Integral RMS Formula

Equation 2

Added on:

Monday, August 17th, 2015