BU7265G_1012 Datasheet, PDF (26/29 Pages) Rohm – Ultra Low Power CMOS Operational Amplifiers

BU7265G,BU7265SG,BU7205HFV,BU7205SHFV,BU7271G,BU7271SG,BU7245HFV,BU7245SHFV,
BU7411G,BU7411SG,BU7421G,BU7421SG,BU7475HFV,BU7475SHFV
Technical Note
●Derating Curve
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.172 (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.172 (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.173(c)-(d) show a derating curve for an example of BU7265 / BU7205 / BU7271 /
BU7245 / BU7411 / BU7421 / BU7475 family.
[W]
Pd(max)
θja ₌ (Tj_‐Ta) / Pd [ _℃ / W]
P2
Ambient temperature Ta ℃]
Package face temperature _{Ta[℃ ]} P1
θja2 <θja1
θja2
θja1
Tj(max)
Pd[W]
Chip surface temperature Tj ℃ ]
0
25
50
75
100
125
Ambient temperature Ta[℃]
(a) Thermal resistance
(b) Derating curve
Fig.172 Thermal resistance and derating
1000
1000
800
600
540[mW]
BU7265G(*23)
BU7271G(*23)
BU7411G(*23)
BU7421G(*23)
800
600
BU7205HFV(*24)
535[mW] BU7245HFV(*24)
BU7475HFV(*24)
400
400
200
200
0
85
0
50
100
150
AMBIENT TEMPERATURE[℃]
(c) BU7265G BU7271G BU7411G BU7421G
1000
0
85
0
50
100
150
AMBIENT TEMPERATURE[℃]
(d) BU7205HFV BU7245HFV BU7475HFV
1000
800
600
540[mW]
BU7265SG(*23)
BU7271SG(*23)
BU7411SG(*23)
BU7421SG(*23)
800
600
535[mW] BU7205SHFV(*24)
BU7245SHFV(*24)
BU7475SHFV(*24)
400
400
200
200
0
105
0
50
100
150
AMBIENT TEMPERATURE[℃]
(e) BU7265SG BU7271SG BU7411SG BU7421SG
0
105
0
50
100
150
AMBIENT TEMPERATURE[℃]
(f) BU7205SHFV BU7245SHFV BU7475SHFV
(*23)
(*24)
Unit
5.4
5.35
[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.173 Derating Curve
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2010.12 - Rev.A