Shindengen Electric MFG.CO.,LTD

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4.6 Cooling design

Tj(max) for the MR4000 Series is 150°C. Since the operation of the MR4000 Series is accompanied by an increase in

temperature associated with power losses, you must carefully consider the type of heat sink needed. Additionally, if the

design must ensure that Tj(max) is not exceeded, you must also consider the thermal shutdown function (TSD = 150°C

(typical)). The extent to which Tj is derated in a design is critical for improving reliability.

Most power losses that occur while the devices in the MR Series operate are associated with the internal

MOSFET. If most power losses are considered ON losses, they may be expressed as follows:

The temperature increase ΔTj attributable to power losses PD is expressed as follows:

equation:

expressed as follows:

heat buildup in the MR Series. This means circuit design must incorporate a cooling design whereby the

temperature is sufficiently derated. Shindengen recommends setting a cooling design target so that the case

temperature will not exceed 100°C.

4.6.1 Junction temperature and power losses

4.6.2 Junction temperature and thermal resistance

Symbol

Unit

Junction-to-ambient thermal

resistance

°C /W

Junction-to-case thermal

resistance

°C /W

Case-to-fin thermal resistance

(contact thermal resistance)

°C /W

Fin-to-ambient thermal resistance

(fin thermal resistance)

°C /W

4.6.3 Cautions for cooling design

4. Design procedure