Datasheet

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15
LTO 50
Vishay Sfernice
Document Number: 50050
Revision 30-May-06
TESTS CONDITIONS TYPICAL DRIFTS
Momentary Overload
EN60115-1
± (0.5 % + 0.005 Ω)
1.5 Pr/5 s
Us < 1.5 UL
EN60115-1
Rapid Temperature Change
IEC 60068-2-14 Tests Na
5 cycles
± (0.5 % + 0.005 Ω)
- 55 °C to + 155 °C
Load Life
EN60115-1
± (1 % + 0.005 Ω)
1000 h Pr at + 25 °C
Humidity (Steady State)
MIL STD 202
± (0.5 % + 0.005 Ω)
Method 103 B Cond. D
Vibration
MIL STD 202
± (0.2 % + 0.005 Ω)
Method 204 Cond. D
Terminal Strength
MIL STD 202
± (0.2 % + 0.005 Ω)
Method 211 Cond. A1
Shock
100G, MIL STD 202
± (0.5 % + 0.005 Ω)
Method 213 Cond. I
PERFORMANCE
Power Resistor Thick Film Technology
Resistance Values ≥ 0.010 ≥ 0.015 ≥ 0.1 ≥ 0.5
Tolerances ± 1 % at ± 10 %
± 900 ppm/°C ± 700 ppm/°C ± 250 ppm/°C ± 150 ppm/°C
SPECIAL FEATURES
Typical Temperature
Coeffi cient
(- 55 °C/+ 150 °C)
P: expressed in W
ΔT: difference between maximum working temperature and room 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.
R
TH: (c-a): thermal resistance value measured between outer side of the resistor and room temperature. It is the
thermal resistance of the heatsink itself (type, shape), the quality of the fastening device, and the thermal resistance of the
thermal compound.
Example:
R
TH: (c-a) for LTO50 power rating 10 W at ambient temperature + 30 °C.
Thermal resistance R
TH (j-c): 2.5 °C/W
Considering equation (1) we have:
ΔT = 155 °C - 30 °C = 125 °C
R
TH (j-c) + RTH (c-a) = = = 12.5 °C/W
R
TH (c-a) = 12.5 °C/W - 2.5 °C/W = 10 °C/W
with a thermal grease R
TH (c - h) = 1 °C/W, we need a heat sink with RTH (h - a) = 9 °C/W.
CHOICE OF THE HEATSINK
The user must choose according to the working conditions of the component (power, room temperature).
Maximum working temperature must not exceed 155 °C. The dissipated power is simply calculated by the following ratio:
P =
ΔT
[R
TH (j-c) + RTH (c-a)]
ΔT
P
125
10
(1)