135D

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Revision: 09-Apr-13

11

Document Number: 40024

THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT

Verifying that the 40 kHz rating does not exceed the peak

voltage limitations:

where:

and:



thus:

Therefore the impressed voltage is:

and:

which is based only on the maximum allowable power

dissipation.

3. Ripple

Current

Multipliers:

The

“Standard

and

Extended Ratings” tables list the maximum permissible

RMS ripple current at 40 kHz for each rating. These

values arebased on the maximum power dissipation

allowed at that frequency.

This ripple current, will cause heating, which adds to the

ambient temperature. The higher ambient temperatures,

voltage derating or current derating is required (see

“Ripple Current Multipliers” tables). Also shown are the

multipliers for ripple currents at various requencies,

caused by the frequency dependence of the (ESR)

equivalent series resistance. (see “Typical ESR as a

Function of Frequency” chart)

I

rated

0.820 A

RMS

=

I

pp rated



0.820 x 2 2

2.32 A

pp

=

=

Z

C (40 kHz)

ESR

40 kHz





2

+ (X

C(40 Hz)





2

=

ESR

40 kHz



4



120 Hz

=

from Extended Ratings table)

1.36



=



X

C (40 kHz)

1

2

fC

-------------

=

1

2

 x 40 x 10

3

 x 25 x 10

-6



-------------------------------------------------------------------------------

0.159



=

=

Z

C 40kHz



1.36



2

+ 0.159



2

1.37



=

=

V

Cpp

Z

1.37

 x 2.32 A

pp

3.18 V

pp

=

=

=

3.18 V

11 V



TYP. ESR AS A FUNCTION OF FREQUENCY

0

0.2

0.6

0.8

0.4

1.4

1.2

1.0

FREQUENCY (Hz)

10

100

1K

40K 100K

10K

1M

RIPPLE CURRENT MULTIPLIERS (120 Hz to 1 kHz)

% OF + 85 °C

RATED PEAK

VOLTAGE

RIPPLE CURRENT MULTIPLIERS

120 Hz

800 Hz

1 kHz

 - 55 °C

+ 85 °C

+ 125 °C

 - 55 °C

+ 85 °C

+ 125 °C

 - 55 °C

+ 85 °C

+ 125 °C

100

0.60

0.39

-

0.71

0.43

-

0.72

0.45

-

90

0.60

0.46

-

0.71

0.55

-

0.72

0.55

-

80

0.60

0.52

-

0.71

0.62

-

0.72

0.62

-

70

0.60

0.58

-

0.71

0.69

-

0.72

0.70

-

 67

0.60

0.60

0.27

0.71

0.71

0.32

0.72

0.72

0.32

RIPPLE CURRENT MULTIPLIERS (10 kHz to 100 kHz)

% OF + 85 °C

RATED PEAK

VOLTAGE

RIPPLE CURRENT MULTIPLIERS

10 kHz

40 kHz

100 kHz

 - 55 °C

+ 85 °C

+ 125 °C

 - 55 °C

+ 85 °C

+ 125 °C

 - 55 °C

+ 85 °C

+ 125 °C

100

0.88

0.55

-

1.0

0.63

-

1.1

0.69

-

90

0.88

0.67

-

1.0

0.77

-

1.1

0.85

-

80

0.88

0.76

-

1.0

0.87

-

1.1

0.96

-

70

0.88

0.85

-

1.0

0.97

-

1.1

1.07

-

 67

0.88

0.88

0.40

1.0

1.0

0.45

1.1

1.1

0.50