Datasheet

www.rohm.com

TSZ02201-0RAR1G200560-1-2

© 2012 ROHM Co., Ltd. All rights reserved.

32/38

30.NOV.2012 Rev.001

TSZ22111･15･001

LMR321G, LMR358xxx, LMR324xxx

0

200

400

600

800

1000

1200

0

255075

100

125

AMBIENT TEMPERATURE [℃]

0

200

400

600

800

1000

1200

0

25

50

75

100

125

AMBIENT TEMPERATURE [℃]

0

200

400

600

800

1000

1200

0

25

50

75

100

125

AMBIENT TEMPERATURE [℃]

(c) LMR321

(d) LMR358

LMR358F(*21)

LMR358FJ(*22)

LMR358FV /FVT(*23)

LMR321G(*20)

LMR324FJ(*25)

LMR324FV(*26)

LMR324FVJ(*27)

(b) Derating curve

●Power Dissipation

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 ship 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 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. Figure 83. (a) shows the model of thermal resistance of the package. Thermal resistance

θja, ambient

temperature Ta, maximum junction temperature Tjmax, and power dissipation Pd can be calculated by the equation below:

θja = (Tjmax-Ta) / Pd

℃/W

・・・・・

(Ⅰ)

Derating curve in Figure 83. (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. Figure 84 (c)-(e) show a derating curve for an example LMR321, LMR358, LMR324.

(*20)

(*21)

(*22)

(*23)

(*24)

(*25)

(*26)

(*27)

(*28)

Unit

5.4

5.52

5.4

5.0

4.7

8.2

7.0

6.8

4.5

mW/℃

When using the unit above Ta=25℃, subtract the value above per degree℃. Permissible dissipation is the value.

When FR4 glass epoxy board 70mm×70mm×1.6mm (cooper foil area below 3％) is mounted.

Figure 83. Thermal resistance and derating

Figure 84. Thermal resistance and derating

(e) LMR324

LMR358FVM/ FVJ(*24)

LMR324F (*28)

(a) Thermal resistance

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)

Power dissipation of LSI [W]

Ambient temperature Ta [℃]

周囲温度 Ta [℃]

チップ 表面温度 Tj [℃]

消費電力 P [W]

Ambient temperature Ta [℃]

Chip surface temperature Tj [℃]

Power dissipation Pd [W]

θja=(Tjmax-Ta)/Pd ℃/W