T491R334K035AS 데이터 시트보기 (PDF) - KEMET

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T491R334K035AS

Surface Mount Capacitors

KEMET 

SOLID TANTALUM CHIP CAPACITORS

TANTALUM MnO2 COMPONENT PERFORMANCE CHARACTERISTICS (con’t.)

XC = 1 ohm

2␲fC

where:

f = frequency, Hertz

C = capacitance, Farad

FIGURE 7a Total Impedance of the Capacitor Below

Resonance

XL = 2␲fL

where:

f = frequency, Hertz

L = inductance, Henries

FIGURE 7b Total Impedance of the Capacitor Above

Resonance

To understand the many elements of a capaci-

tor, see Figure 8.

ESR — Represents the actual ohmic series resis-

tance in series with the capacitance. Lead wires

and capacitor electrodes are contributing sources.

RL — Capacitor Leakage Resistance. Typically it

can reach 50,000 megohms in a tantalum capaci-

tor. It can exceed 1012 ohms in monolithic ceram-

ics and in film capacitors.

Rd — The dielectric loss contributed by dielectric

absorption and molecular polarization. It becomes

very significant in high frequency measurements

and applications. Its value varies with frequency.

Cd — The inherent dielectric absorption of the

solid tantalum capacitor which typically equates to

1-2% of the applied voltage.

As frequency increases, XC continues to decrease

according to its equation above. There is unavoid-

able inductance as well as resistance in all capaci-

tors, and at some point in frequency, the reac-

tance ceases to be capacitive and becomes

inductive. This frequency is called the self-reso-

nant point. In solid tantalum capacitors, the reso-

nance is damped by the ESR, and a smooth,

rather than abrupt, transition from capacitive to

inductive reactance follows.

Typical ESR/Z frequency response curves are

shown in Figures 9a and 9b. These curves are

for selected ratings and represent typical T491

Series performance. Maximum limits for 100 kHz

ESR are listed in the part number tables for

each series. Note that the T494 Series offers low

ESR and the T495 Series is specially designed

for very low ESR performance. Refer to page 31

for more information. See also KEMET’s T510

Series low ESR ratings on page 40.

ESL

ESR

C

RL

Cd

Rd

FIGURE 8 The Real Capacitor

A capacitor is a complex impedance consisting of

many series and parallel elements, each adding

to the complexity of the measurement system.

ESL — Represents lead wire and construction

inductance. In most instances (especially in solid

tantalum and monolithic ceramic capacitors) it is

FIGURE 9a ESR & Impedance (Z) vs Frequency

insignificant at the basic measurement frequen-

cies of 120 and 1000 Hz.

8

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

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