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Thermal characterist ics: how to choose the

heat-sink

Sometimes the GS-R1012 requires an external

heat-sink depending both operating temperature

conditions and power.

Before entering into calculations details, some ba-

sic concepts will be explained to better understand

the problem.

The thermal resistance between two points is rep-

resented by their temperature difference in front of

a specified dissipated power, and it is expressed in

Degree Centigrade per Watt (

°C/W).

For GS-R1012 the thermal resistance case to am-

bient is 7.5

°C/W. This means that an internal power

dissipation of 1W will bring the case temperature at

7.5

°C above the ambient temperature.

The maximum case temperature to which the mod-

ule provides 10A is 75

°C (see fig. 6).

Let’s suppose to have a GS-R1012 that delivers a

load current of 10A at an ambient temperature of

40

°C.

The dissipated power in this operating condition is

about 10.4W (at typical efficiency of 92%), and the

case temperature of the module will be:

This value exceeds the maximum allowed tempera-

ture and an external heat-sink must be added. To

this purpose four holes (see mechanical drawing)

are provided on the metal surface of the module.

To calculate this heat-sink, let’s first determine what

the total thermal resistance should be.

10.4

= 3.37°C/ W

This value is the resulting value of the additional

heatsink thermal resistance.

Figure 3.

Figure 4.

GS-R1012