Technical Note
BA2904YF-C,BA2904YFVM-C,BA2902YF-C,BA2902YFV-C
●Derating curves
Power dissipation(total loss) indicates the power that can be consumed by IC at Ta=25℃(normal temperature). IC is heated
when it consumed power, and the temperature of IC chip becomes higher than ambient temperature. The temperature that
can be accepted by IC chip depends on circuit configuration, manufacturing process, and consumable power is limited.
Power dissipation is determined by the temperature allowed in IC chip(maximum junction temperature) and thermal
resistance of package(heat dissipation capability). The maximum junction temperature is typically equal to the maximum
value in the storage temperature range. Heat generated by consumed power of IC radiates from the mold resin or lead frame
of the package. The parameter which indicatesthis heat dissipation capability(hardness of heat release)is called thermal
resistance, represented by the symbol θja[℃/W].The temperature of IC inside the package can be estimated by this thermal
resistance. Fig.54(a) shows the model of thermal resistance of the package. Thermal resistance θja, ambient temperature Ta,
junction temperature Tj, and power dissipation Pd can be calculated by the equation below:
θja = (Tj-Ta) / Pd
[℃/W]
・・・・・ (Ⅰ)
Derating curve in Fig.54(b) indicates power that can be consumed by IC with reference to ambient temperature.Power that
can be consumed by IC begins to attenuate at certain ambient temperature. This gradient iis determined by thermal
resistance θja. Thermal resistance θja depends on chip size, power consumption, package,ambient temperature, package
condition, wind velocity, etc even when the same of package is used.
Thermal reduction curve indicates a reference value measured at a specified condition. Fig.55(c),(d) show a derating curve
for an example of BA2904Y, BA2902Y.
LSI
[W]
n of LSI
の消費電力
Power dissipa
tio
Pd (max)
θja = ( Tj Ta ) / Pd
[ /W]
℃
ー
P2
θja2 < θja1
θ' ja2
Ambient temperature
Ta [
℃
]
周囲温度
P1
θ ja2
Tj ' (max) Tj (max)
θ' ja1
θ ja1
Chip surface temperature Tj [
]
チップ表面温度
℃
0
25
50
75
周囲温度
100
℃
125
150
Power dissipation Pd[W]
消費電力 P [W]
Ambient temperature Ta [
]
(b) Derating curve
(a) Thermal resistance
Fig. 54 Thermal resistance and derating
1000
800
600
400
200
0
1000
870mW(*8)
780mW(*6)
590mW(*7)
BA2902YFV-C
800
BA2904YF-C
610mW(*9)
BA2902YF-C
600
400
200
0
BA2904YFVM-C
0
25
50
75
100
125
150
0
25
50
75
100
125
150
AMBIENT TEMPERATURE [
]
AMBIENT TEMPERATURE [
]
℃
℃
(c) BA2904Y family
(d) BA2902Y family
(*6)
6.2
(*7)
4.8
(*8)
7.0
(*9)
4.9
Unit
[mW/℃]
When using the unit above Ta=25[℃], subtract the value above per degree [℃].
Permissible dissipation is the value when FR4 glass epoxy board 70[mm]×70[mm]×1.6[mm](cooper foil area below 3[%]) is mounted.
Fig. 55 Derating curve
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2011.08 - Rev.B
11/16
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