Technical Note

BA10358F/FV,BA10324AF/FV,BA2904SF/FV/FVM,BA2904F/FV/FVM,BA2904HFVM-C,

BA2902SF/FV/KN,BA2902F/FV/KN,BA3404F/FVM

21/24

www.rohm.com

2009.05 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

●

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.124(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.124(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.125(a)～(d) show a derating

curve for an example of BA10358, BA10324A, BA2904S, BA2904, BA2904HFVM-C, BA3404, BA2902S, BA2902.

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.

（

*9）

（

*10）

（

*11)

（

*12）

（

*13）

（

*14）

（

*15）

（

*16）

（

*17）

（

*18）

Unit

6.2

5.5

7.0

4.9

6.2

5.5

4.8

7.0

5.3

4.9

[mW/℃]

(a) Thermal resistance

(b) Derating curve

Fig. 124 Thermal resistance and derating curve

Fig. 125 Derating curve

0

50

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)

Ambient temperature

Power dissipation of LSI

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]

Ambient temperature

Chip surface temperature

Power dissipation

0

200

400

600

800

1000

0

25

50

75

100

125

周囲温度　Ta　[℃]

BA10358F

BA10358FV

620mW (*1)

550mW (*2)

(a) BA10358 ファミリ

0

200

400

600

800

1000

0

25

50

75

100

125

周囲温度　Ta　[℃]

BA10324AFV

BA10324AF

700mW (*3)

490mW (*4)

(a) BA10324A ファミリ

0

200

400

600

800

1000

0

25

50

75

100

125

150

周囲温度　Ta　[℃]

BA2904F

BA3404F

BA2904FV

BA2904FVM

BA3404FVM

780mW( *5)

690mW( *6)

590mW (*7)

BA3404F

BA3404FVM

(a) BA2904 ファミリ

0

200

400

600

800

1000

0

25

50

75

100

125

150

周囲温度　Ta　[℃]

BA2902FV

BA2902KN

BA2902F

870mW( *8)

660mW( *9)

610mW (*10)

(a) BA2902 ファミリ

(d)BA2902S/BA2902 family

Ambient temperature ：Ta [℃]

550mW(*10)

620mW(*9)

700mW(*11)

490mW(*12)

870mW(*16)

660mW(*17)

610mW(*18)

BA2902SFV

BA2902SKN

BA2902SF

105

105

(b)

Ambient temperature ：Ta [℃]

Ambient temperature ：Ta [℃]

(a)BA10358 family

(b)BA10324A family

0

200

400

600

800

1000

0

255075

100

125

150

AMBIENT TEMPERATURE [℃]

BA2904F

BA2904FV

BA2904FVM

BA2904HFVM-C

BA2904SFV

BA2904SFVM

105

BA2904SF

690mW(*14)

780mW(*13)

590mW(*15)

BA3404F

BA3404FVM

Ambient temperature ：Ta [℃]

(c)BA2904S/BA2904/BA3404 family,BA2904H

50

400

200

800

600

0

1000

25

75

100

125

150

0