C&H Technology LTO30 - Manual (Page 3)

www.vishay.com For technical questions, contact: [email protected] Document Number: 50049
2 Revision: 16-Oct-08
LTO 30
Vishay Sfernice 30 W Power Resistor Thick Film Technology
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 150 °C. The dissipated power is simply calculated by the following ratio:
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) and the quality of the fastening device, and the thermal resistance
of the thermal compound.
Example:
R
TH
(c - a) for LTO 30 power rating 10 W at ambient temperature + 25 °C
Thermal resistance R
TH
(j - c): 4.2 °C/W
Considering equation (1) we have:
ΔT = 150 °C - 25 °C = 125 °C
R
TH
(j - c) + R
TH
(c - a) = = = 12.5 °C/W
R
TH
(c - a) = 12.5 °C/W - 4.2 °C/W = 8.3 °C/W
with a thermal grease R
TH
(c - h) = 1 °C/W, we need a heatsink with R
TH
(h - a) = 7.3 °C/W.
PERFORMANCE
TESTS CONDITIONS REQUIREMENTS
Momentary Overload
EN 60115-1
1.5 Pr/5 s
U
S
< 1.5 U
L
± (0.5 % + 0.005 Ω)
Rapid Temperature Change
EN 60115-1
IEC 60068-2-14 Tests Na
5 cycles
- 55 °C to + 155 °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 + 155 °C)
± 900 ppm/°C ± 700 ppm/°C ± 250 ppm/°C ± 150 ppm/°C
P
ΔT
R
TH
j c –
( ) R
TH
c a –
( ) + [ ]
----------------------------------------------------------------------
1 ( )
=
ΔT
P
-------
125
10
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