Max AC Rating for DC Rated MLCCs
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Fort Lauderdale, FL 33301 USA • 954-766-2800 • www.kemet.com
KEMET’s Surface Mount Device (SMD) Multilayer Ceramic Capacitors (MLCCs) are normally rated at DC voltages. However,
in many cases, applications require AC voltages that can be high enough to cause degradation. The below rules can be used
to convert the DC rated voltage to max allowable AC voltage.
Voltage Rule
Definitions:
• V
rated DC
: DC rated voltage of MLCC
• Vp: Peak voltage of AC waveform
• Vpp: Peak to Peak voltage of AC waveform
• Vrms: RMS voltage of AC waveform
• Vdc: DC voltage of AC waveform (offset)
When calculating the AC rated voltage of an MLCC, both Rule #1 and Rule #2 below must be followed.
Rule #1 (Sinusoidal)
Rule #2 (Sinusoidal)
Rule #3 (Pulse)
Current Rule
In addition to the rules above, the self-temperature rise (T
rise
) of the MLCC must be below 20
o
C under normal operating
conditions.
Definitions:
• R
Θ
: Thermal Resistance of MLCC
• I: RMS current through the MLCC
• P: Dissipated Power
• T
rise
: Self-Temperature Rise (dT)
• ESL: Equivalent Series Inductance
• ESR: Equivalent Series Resistance
• C: Capacitance