APPLICATION NOTES FOR MULTILAYER

CERAMIC CAPACITORS

ELECTRICAL CHARACTERISTICS

The fundamental electrical properties of multilayer

ceramic capacitors are as follows:

Polarity: Multilayer ceramic capacitors are not polar,

and may be used with DC voltage applied in either direction.

Rated Voltage: This term refers to the maximum con-

tinuous DC working voltage permissible across the entire

operating temperature range. Multilayer ceramic capacitors

are not extremely sensitive to voltage, and brief applications

of voltage above rated will not result in immediate failure.

However, reliability will be reduced by exposure to sustained

voltages above rated.

Capacitance: The standard unit of capacitance is the

farad. For practical capacitors, it is usually expressed in

microfarads (10-6 farad), nanofarads (10-9 farad), or picofarads

(10-12 farad). Standard measurement conditions are as

follows:

Class I (up to 1,000 pF):

Class I (over 1,000 pF):

Class II:

Class III:

1MHz and 1.2 VRMS

maximum.

1kHz and 1.2 VRMS

maximum.

1 kHz and 1.0 ± 0.2 VRMS.

1 kHz and 0.5 ± 0.1 VRMS.

The variation of a capacitor’s impedance with frequency

determines its effectiveness in many applications.

Dissipation Factor: Dissipation Factor (DF) is a mea-

sure of the losses in a capacitor under AC application. It is the

ratio of the equivalent series resistance to the capacitive reac-

tance, and is usually expressed in percent. It is usually mea-

sured simultaneously with capacitance, and under the same

conditions. The vector diagram in Figure 2 illustrates the rela-

tionship between DF, ESR, and impedance. The reciprocal of

the dissipation factor is called the “Q”, or quality factor. For

convenience, the “Q” factor is often used for very low values

of dissipation factor. DF is sometimes called the “loss tangent”

or “tangent ␦”, as derived from this diagram.

Figure 2

DF

=

ESR

Xc

Xc =

1

2πfC

ESR

O

δ

Xc

Ζ

Like all other practical capacitors, multilayer ceramic

capacitors also have resistance and inductance. A simplified

schematic for the equivalent circuit is shown in Figure 1.

Other significant electrical characteristics resulting from

these additional properties are as follows:

Figure 1

R

P

L

C = Capacitance

L = Inductance

R

S

C

R = Equivalent Series Resistance (ESR)

S

R = Insulation Resistance (IR)

P

Impedance: Since the parallel resistance (Rp) is nor-

mally very high, the total impedance of the capacitor is:

Z=

RS2+ (XC - XL)2

Where Z = Total Impedance

RS = Equivalent Series Resistance

XC = Capacitive Reactance

=

1

2πfC

XL = Inductive Reactance = 2πfL

Insulation Resistance: Insulation Resistance (IR) is the

DC resistance measured across the terminals of a capacitor,

represented by the parallel resistance (Rp) shown in Figure 1.

For a given dielectric type, electrode area increases with

capacitance, resulting in a decrease in the insulation resis-

tance. Consequently, insulation resistance is usually specified

as the “RC” (IR x C) product, in terms of ohm-farads or

megohm-microfarads. The insulation resistance for a specific

capacitance value is determined by dividing this product by

the capacitance. However, as the nominal capacitance values

become small, the insulation resistance calculated from the

RC product reaches values which are impractical.

Consequently, IR specifications usually include both a mini-

mum RC product and a maximum limit on the IR calculated

from that value. For example, a typical IR specification might

read “1,000 megohm-microfarads or 100 gigohms, whichever

is less.”

Insulation Resistance is the measure of a capacitor to

resist the flow of DC leakage current. It is sometimes referred

to as “leakage resistance.” The DC leakage current may be

calculated by dividing the applied voltage by the insulation

resistance (Ohm’s Law).

Dielectric Withstanding Voltage: Dielectric withstand-

ing voltage (DWV) is the peak voltage which a capacitor is

designed to withstand for short periods of time without dam-

age. All KEMET multilayer ceramic capacitors will withstand a

test voltage of 2.5 x the rated voltage for 60 seconds.

KEMET specification limits for these characteristics at

standard measurement conditions are shown in Table 1 on

page 4. Variations in these properties caused by changing

conditions of temperature, voltage, frequency, and time are

covered in the following sections.

© KEMET Electronics Corporation, P.O. Box 5928, Greenville, S.C. 29606, (864) 963-6300

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