D2TO35

www.vishay.com

Vishay Sfernice

Revision: 22-Apr-13

3

Document Number: 51058

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

CHOICE OF THE BOARD

The user must choose the board according to the working conditions of the component (power, room temperature). Maximum

working temperature must not exeed 175 °C. The dissipated power is simply calculated by the following ratio:

P:

Expressed in W

T:

Difference between maximum working temperature and room temperature or fluid cooling temperature

of the component: 4.28 °C/W.

thermal resistance of the solder layer.

Example:

Considering equation (1) we have:



T = 175 °C - 25 °C = 150 °C

Single Pulse:

These informations are for a single pulse on a cold resistor at 25 °C (not already used for a dissipation) and for pulses of

100 ms maximum duration.

The formula used to calculate E is:

with:

E (J): Pulse energy

P (W): Pulse power

t (s): Pulse duration

U (V): Pulse voltage

R (W): Resistor

The energy calculated must be less: than that allowed by the graph.

Repetitive or Superimposed Pulses:

The following formula is used to calculate the “equivalent” energy of a repetitive pulse or the “equivalent energy” of a pulse on

a resistor that is already dissipating power.

with:

Equivalent pulse energy

E (J):

Known pulse energy

Resistor power rating

Mean power being dissipated

continuous power of resistor.

P

T

R

TH (j - c)



R

TH (c - h)



R

TH (h - a)



++

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

1



=

E

U

2

R

--------

==

E

c

P

a

P

r

------

+





=