bu7265g ROHM Co. Ltd., bu7265g Datasheet - Page 15

• Manufacturer Part Number: bu7265g
• Description: General-purpose Operational Amplifier / Comparator Series
• Manufacturer: ROHM Co. Ltd.

●Derating Curve
BU7265G,BU7265SG,BU7271G,BU7271SG,
BU7411G,BU7411SG,BU7421G,BU7421SG
© 2010 ROHM Co., Ltd. All rights reserved.
www.rohm.com
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 θj-a[℃/W]. The temperature of IC inside the package can be estimated by
this thermal resistance.
Fig.98 (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 :
Derating curve in Fig.98 (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 is 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.99(c)-(d) show a derating curve for an example of BU7265 family, BU7271family,
BU7411family, BU7421family.
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
θja = (Tj － Ta) / Pd [ ℃ / W]
Chip surface temperature Tj[
1/θja
5.4
800
600
400
200
Ambient temperature Ta[ ℃ ]
0
(a) Thermal resistance
Power dissipation Pd[W]
0
(c) BU7265G BU7271G
θja = (Tj－Ta) / Pd
BU7411G BU7421G
AMBIENT TEMPERATURE [℃]
50
Package face temperature Ta[ ℃ ]
Fig.98 Thermal resistance and derating
540[mW]
85
℃
100
[mW/℃]
]
Unit
150
[℃/W]
Fig.99 Derating Curve
15/17
・・・・・ (Ⅰ)
800
600
400
200
P2
P1
0
0
0
(d) BU7265SG BU7271SG
(b) Derating curve
Pd(max)
BU7411SG BU7421SG
AMBIENT TEMPERATURE [ ℃ ]
25
[W]
Ambient temperatureTa[ ℃ ]
50
θja1
50
540［mW］
75
100
θja2 <θja1
105
100
θja2
125
150
Tj(max)
BU7265/BU7271
BU7411/BU7421
BU7411/BU7421
Technical Note
150
2010.03 - Rev.A
Tj(max)