TAJB335016 datasheet(35/51 Pages) AVX

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Technical Summary and

Application Guidelines

Table I: Power Dissipation Ratings (In Free Air)

TAJ/TPS/CWR11

TAZ/CWR09

Series Molded Chip

2.1 RIPPLE RATINGS (A.C.)

In an a.c. application heat is generated within the capacitor

by both the a.c. component of the signal (which will depend

upon the signal form, amplitude and frequency), and by the

d.c. leakage. For practical purposes the second factor is

insignificant. The actual power dissipated in the capacitor is

calculated using the formula:

P =

I 2 R

and

rearranged to I =

(P⁄

.....(Eq. 1)

and substituting

P =

E2 R

where

I = rms ripple current, amperes

R = equivalent series resistance, ohms

E = rms ripple voltage, volts

P = power dissipated, watts

Z = impedance, ohms, at frequency under

consideration

Maximum a.c. ripple voltage (E

max).

From the previous equation:

max =

(P⁄

.....(Eq. 2)

Where P is the maximum permissible power dissipated as

listed for the product under consideration (see tables).

However care must be taken to ensure that:

1. The d.c. working voltage of the capacitor must not be

exceeded by the sum of the positive peak of the applied

a.c. voltage and the d.c. bias voltage.

2. The sum of the applied d.c. bias voltage and the negative

peak of the a.c. voltage must not allow a voltage reversal

in excess of the “Reverse Voltage”.

Historical ripple calculations.

Previous ripple current and voltage values were calculated

using an empirically derived power dissipation required to

give a 10°C rise of the capacitors body temperature from

room temperature, usually in free air. These values are shown

in Table I. Equation 1 then allows the maximum ripple current

to be established, and Equation 2, the maximum ripple

voltage. But as has been shown in the AVX article on thermal

management by I. Salisbury, the thermal conductivity of a

Tantalum chip capacitor varies considerably depending upon

how it is mounted.

Case

Max. power

size

dissipation (W)

0.075

0.085

0.110

0.150

0.165

0.090

0.130

0.055

0.065

0.080

0.250

Case

Max. power

size

dissipation (W)

0.050

0.070

0.075

0.080

0.090

0.100

0.125

0.150

Temperature

derating factors

Temp. °C

Factor

+25

1.0

+55

0.90

+85

0.80

+125

0.16

Temperature correction factor

for ripple current

Temp. °C

Factor

+25

1.0

+55

0.95

+85

0.90

+125

0.40

√

SECTION 2

A.C. OPERATION, RIPPLE VOLTAGE AND RIPPLE CURRENT

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