Technical Note

19/24

BA10393F,BA10339F,BA10339FV,BA2903SF,BA2903SFV,BA2903SFVM,BA2903F,BA2903FV,

BA2903FVM,BA2901SF,BA2901SFV,BA2901SKN,BA2901F,BA2901FV,BA2901KN,BA8391G

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2011.08 - Rev.B

© 2011 ROHM Co., Ltd. All rights reserved.

0

200

400

600

800

1000

025

50

75

100

125

周囲温度　

Ta　 [°C]

0

200

400

600

800

1000

0

25

50

75

100

125

150

周囲温度　

Ta　 [°C]

0

200

400

600

800

1000

0

25

50

75

100

125

150

周囲温度　

Ta　 [°C]

0

200

400

600

800

1000

0

25

50

75

100

125

周囲温度　

Ta　 [°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 indicates this 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.114 (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.114 (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.115(c) ~ (f) shows a derating curve for an example of BA8391, BA10393, BA10339,

BA2903S, BA2903, BA2901S, and BA2901.

(*16)

(*17)

(*18)

(*19)

(*20)

(*21)

(*22)

(*23)

(*24)

Unit

6.2

7.0

4.9

6.2

5.5

4.7

7.0

5.3

4.9

[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.

105

105

0

200

400

600

800

1000

0

25

50

75

100

125

BA2903F

BA10339FV

BA10339F

BA2901KN

Ambient Temperature [℃]

Ambient Temperature [℃]

Fig.115 Derating curve

Fig.114 Thermal resistance and derating curve

(c)BA10393 family

(d)BA10339 family

(e)BA2903 family

(f)BA2901 family

BA10393F

BA2903FV

BA2903FVM

BA2901FV

BA2901F

BA2903SFV

BA2903SF

BA2903SFVM

BA2901SFV

BA2901SKN

BA2901SF

(b) Derating curve

(a) Thermal resistance

周囲温度 Ta [℃]

チ ップ 表面温度 Tj [℃]

消費電力 P [W]

θja = ( Tj ーTa ) / Pd [℃/W]

Chip surface temperature

Power dissipation

Ambient temperature

050

75

100

125

150

25

P1

P2

Pd (max)

LSIの消費電力 [W]

θ' ja2

θ' ja1

Tj ' (max)

θja2 < θja1

周囲温度

Ta [℃ ]

θ ja2

θ ja1

Tj (max)

Power dissipation of LSI

Ambient temperature

Ambient Temperature [℃]

Ambient Temperature [℃]