Document Number: 50051 For technical questions, contact: sfer@vishay.com www.vishay.com
Revision: 27-Aug-10 81
LTO 100
Power Resistor Thick Film Technology Vishay Sfernice
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 175 °C. The dissipated power is simply calculated by the following ratio:
P: Expressed in W
ΔT: Difference between maximum working temperature and room temperature
RTH (j - c): Thermal resistance value measured between resistive layer and outer side of the resistor. It is the thermal
resistance of the component.
RTH (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) and the quality of the fastening device, and the thermal resistance
of the thermal compound.
Example:
RTH (c - a) for LTO 100 power rating 10 W at ambient temperature + 25 °C
Thermal resistance RTH (j - c): 1.5 °C/W
Considering equation (1) we have:
ΔT = 175 °C - 25 °C = 150 °C
RTH (j - c) + RTH (c - a) = = = 15 °C/W
RTH (c - a) = 15 °C/W - 1.5 °C/W = 13.5 °C/W
with a thermal grease RTH (c - h) = 1 °C/W, we need a heatsink with RTH (h - a) = 12.5 °C/W.
PERFORMANCE
TESTS CONDITIONS REQUIREMENTS
Momentary Overload
EN 60115-1
1.5 Pr/5 s
US < 1.5 UL
± (0.5 % + 0.005 Ω)
Rapid Temperature Change
EN 60115-1
IEC 60068-2-14 Test Na
5 cycles
- 55 °C to + 175 °C
± (0.5 % + 0.005 Ω)
Load Life EN 60115-1
1000 h Pr at + 25 °C ± (1 % + 0.005 Ω)
Humidity (Steady State) MIL STD 202
Method 103 B Cond. D ± (0.5 % + 0.005 Ω)
Vibration MIL STD 202
Method 204 Cond. D ± (0.2 % + 0.005 Ω)
Terminal Strength MIL STD 202
Method 211 Cond. A1 ± (0.2 % + 0.005 Ω)
Shock 100G, MIL STD 202
Method 213 Cond. I ± (0.5 % + 0.005 Ω)
SPECIAL FEATURES
Resistance Values ≥ 0.010 ≥ 0.015 ≥ 0.1 ≥ 0.5
Tolerances ± 1 % at ± 10 %
Typical Temperature Coefficient
(- 55 ° to + 175 °C) ± 900 ppm/°C ± 700 ppm/°C ± 250 ppm/°C ± 150 ppm/°C
P = ΔT
RTH (j - c) + RTH (c - a)
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