HUGD-50 Datasheet, PDF (5/13 Pages) –

Hi-Rel
HUGD-50 Series ^Grade
8- Thermal Characteristics
Characteristics
Conditions
Limit or typical
Operating ambient temperature
range at full load
Ambient temperature *
Minimum
Maximum
Operating case temperature
range at full load
Case temperature
Minimum
Maximum
Storage temperature range
Non functionning
Minimum
Maximum
Thermal resistance
Rth case to ambient in free air
natural convection
Typical
Note * : The upper temperature range depends on configuration, the user must assure a max. case temperature of + 105°C.
Performances
- 40°C
+ 85°C
- 40°C
+105°C
- 55°C
+ 125°C
12°C /W
The HUGD-50 series operating case temperature must not exceed 105°C. The maximum ambient temperature admissible for
the DC/DC converter corresponding to the maximum operating case temperature of 105°C depends on the ambient airflow,
the mounting/orientation, the cooling features and the power dissipated.
To calculate a maximum admissible ambient temperature the following method can be used. Knowing the maximum case
temparature Tcase = 105°C of the module, the power used Pout and the efficiency η :
• determine the power dissipated by the module Pdiss that should be evacuated :
Pdiss = Pout(1/η - 1)
• determine the maximum ambient temperature :
Ta = 105°C - Rth x Pdiss
where Rth is the thermal resistance from the case to ambient.
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The previous thermal calculation shows two areas of operation :
• a normal operation area in a free natural ambient convection (grey area in this following graph),
• an area with cooling features (air flow or heatsink) ensuring a maximum case temperature below the maximum
operating case temperature of 105°C (white area in the following graph).
Power (W)
100%
75%
50%
25%
Additionnal cooling operation area
Natural convection operation area
10 20 30 40 50 60 70 80 90 100 110
Temperature (˚C)
Full load ambient temperature without derating : 85˚C
Maximum case temperature : 105˚C
Maximum storage temperature : 125˚C
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