BD6973FV-LB 데이터 시트보기 (PDF) - ROHM Semiconductor
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BD6973FV-LB Datasheet PDF : 20 Pages
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BD6973FV-LB
Datasheet
Power Dissipation
1. Power Dissipation
Power dissipation (total loss) indicates the power that can be consumed by IC at Ta=25°C (normal temperature). IC is
heated when it consumes power, and the temperature of IC chip becomes higher than ambient temperature. The
temperature that can be accepted by IC chip into the package, that is junction temperature of the absolute maximum
rating, depends on circuit configuration, manufacturing process, etc. Power dissipation is determined by this maximum
joint temperature, the thermal resistance in the state of the substrate mounting, and the ambient temperature.
Therefore, when a power dissipation that provides by the absolute maximum rating is exceeded, the operating
temperature range is not a guarantee. The maximum junction temperature is in general equal to the maximum value in
the storage temperature range.
2. Thermal Resistance
Heat generated by consumed power of IC is radiated from the mold resin or lead frame of package. The parameter
which indicates this heat dissipation capability (hardness of heat release) is called thermal resistance. In the state of
the substrate mounting, thermal resistances from the chip junction to the ambience and to the package surface are
shown respectively with θja[°C/W] and θjc[°C/W]. Thermal resistance is classified into the package part and the
substrate part, and thermal resistance in the package part depends on the composition materials such as the mold
resins and the lead frames. On the other hand, thermal resistance in the substrate part depends on the substrate heat
dissipation capability of the material, the size, and the copper foil area etc. Therefore, thermal resistance can be
decreased by the heat radiation measures to install the heat sink etc. in the mounting substrate.
The thermal resistance model and calculations are shown in Figure 33, and Equation 1 and 2, respectively.
ja
Tj
Ta
P
[C/W] (Equation 1)
jc
Tj
Tc
P
[C/W] (Equation 2)
where:
θja is the thermal resistance from the chip junction
to the ambience
θjc is the thermal resistance from the chip junction
to the package surface
Tj is the junction temperature
Ta is the ambient temperature
Tc is the package surface temperature
P is the power consumption
Ambient Temperature Ta[°C]
θja[°C/W]
Package Surface
Temperature Tc[°C]
Junction Temperature Tj[°C]
θjc[°C/W]
Mounting Substrate
Figure 33. Thermal Resistance Model of Surface Mount
Even if it uses the same package, thermal resistance θja and θjc are changed depending on the chip size, power
consumption, and the measurement environments of the ambient temperature, the mounting condition, and the wind
velocity, etc. Thermal resistance under a certain regulated condition is shown in Table 1 as a reference data when the
FR4 glass epoxy substrate (70mm x 70mm x 1.6mm and 3% or less in the area of the copper foil) is mounted.
Table 1. Thermal Resistance (Reference Data)
Rohm Standard (Note 1)
One-layer
Unit
θja
142.9
°C/W
θjc
36
°C/W
(Note 1) 70.0mm x 70.0mm x 1.6mm FR4 glass epoxy substrate
3. Thermal De-rating Curve
Thermal de-rating curve indicates power that can be
1.0
consumed by IC with reference to ambient
temperature. Power that can be consumed by IC
0.8
begins to attenuate at certain ambient temperature
(25°C), and becomes 0W the maximum joint
0.6
temperature (150°C). The inclination is reduced by
the reciprocal of thermal resistance θja. The thermal
0.4
de-rating curve under a certain regulated condition
is shown in Figure 34.
0.2
–1/θja=–7.0mW/°C
Operating Range
0.0
-50 -25 0
25 50 75 100 125 150
Ambient Temperrature: Ta[°C]
Figure 34. Power Dissipation vs Ambient Temperature
(70.0mm x 70.0mm x 1.6mm glass epoxy substrate)
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© 2013 ROHM Co., Ltd. All rights reserved.
TSZ22111・15・001
12/17
TSZ02201-0H1H0B100820-1-2
27.Feb.2014 Rev.002
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