Datasheet
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© May 2016
Würth Elektronik eiSos GmbH & Co. KG - Data Sheet - REV 1.0
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WPMDU1251501 / 171021501
MagI³C Power Module
VDRM - Variable Step Down Regulator Module
Determine power losses and thermal requirements of the board
For example:
T
AMB(MAX)
is the maximum air temperature surrounding the module.
T
J(MAX)
is the maximum value of the junction temperature according to the “OPERATING CONDITIONS” limit.
The goal of the calculation is to determine the characteristics of the required heat sink. In case of a surface mounted
module this would be the PCB (number of layers, copper area and thickness). These characteristics are reflected in the
value of the thermal resistance case to ambient:
.
The basic formula for calculating the operating junction temperature T
J
of a semiconductor device is as follows:
(14)
P
IC-LOSS
are the total power losses within the module IC and are related to the operating conditions.
is the thermal resistance junction to ambient and calculated as:
(15)
is the thermal resistance junction to case.
Combining equation (14) and (15) results in the maximum case-to-ambient thermal resistance:
(16)
From section ”THERMAL SPECIFICATIONS“ use as typical thermal resistance from junction to case
=
= 6.8
°C/W. Use the 25°C power dissipation curves in the “TYPICAL PERFORMANCE CURVES“ section to estimate the P
IC-
LOSS
for the application being designed. Add 20% losses to take into consideration the ambient temperature of 85°C.