D2TO20_15 Datasheet, PDF (3/6 Pages) Vishay Siliconix – Surface Mount Power Resistor Thick Film Technology

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D2TO20
Vishay Sfernice
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 exceed 175 °C. The dissipated power is simply calculated by the following ratio:
P = -------------------------------------------^----^T--------------------------------------------^{1}
R_{TH (j - c)} + R_{TH (c - h)} + R_{TH (h - a)}
P:
Expressed in W
T:
Difference between maximum working temperature and room temperature or fluid cooling temperature
R_{TH (j - c)}: Thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal resistance
of the component: 6.5 °C/W.
R_{TH (c - h)}: Thermal resistance value measured between outer side of the resistor and upper side of the board. This is the thermal
resistance of the solder layer.
R_{TH (h - a)}: Thermal resistance of the board.
Example:
R_{TH (c - h)} + R_{TH (h - a)} for D2TO20 power rating 2.5 W at ambient temperature +25 °C.
Thermal resistance R_{TH (j - c)}: 6.5 °C/W
Considering equation ⁽¹⁾ we have:
T = 155 °C - 25 °C = 130 °C
R_{TH (j - c)} + R_{TH (c - h)} + R_{TH (h - a)} = T/P = 130/2.5 = 52 °C/W
R_{TH (c - h)} + R_{TH (h - a)} = 52 °C/W - 6.5 °C/W = 45.5 °C/W
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 = P x t = -^U-----²- x t
R
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.
Revision: 10-Feb-15
3
Document Number: 51055
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