bu7252sfvm ROHM Co. Ltd., bu7252sfvm Datasheet - Page 14

• Manufacturer Part Number: bu7252sfvm
• Description: Comparators Low Voltage Cmos
• Manufacturer: ROHM Co. Ltd.

● 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.6 (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.6 (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. Fig7(c)-(f) show a derating curve for an example of BU7251family, BU7252 family, BU7231
family, BU7232 family.
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.
（*8）
5.4
θja = ( Tj ー Ta ) / Pd [ ℃ /W]
Chip surface temperature Tj [ ℃ ]
800
600
400
200
(a) Thermal resistance
Ambient temperature Ta [ ℃ ]
800
600
400
200
0
0
θja ＝ (Tj－Ta) / Pd
Power dissipation P [W]
（*9） （*10）
0
0
6.2
(e) BU7251SG BU7231SG
(c) BU7251G BU7231G
AMBIENT TEMPERATURE [ ℃ ]
AMBIENT TEMPERATURE [ ℃ ]
50
4.8
50
Fig6. Thermal resistance and power dissipation
540[mw]
540[mw]
[mW/℃]
85
Unit
100
100
BU7251G(*8)
BU7231G(*8)
BU7251SG(*8)
BU7231SG(*8)
105
[℃/W]
Fig7. Derating curve
150
150
14/16
・・・・・ （Ⅰ）
Power dissipation Pd:[W]
P2
P1
LSI の消費電力 [W]
1000
1000
800
600
400
200
(f) BU7252S F/FVM BU72432S F/FVM
800
600
400
200
0
(d) BU7252F/FVM BU7232F/FVM
Ambient temperature:Ta[ ℃ ]
0
0
0
0
Pd(max)
周囲温度 Ta[ ℃ ]
(b) Derating curve
25
AMBIENT TEMPERATURE [ ℃ ]
AMBIENT TEMPERATURE [ ℃ ]
50
50
50
θja1
480[mw]
620[mw]
480[mw]
620[mw]
85
75
BU7252SFVM(*10)
BU7232SFVM(*10)
BU7252SF(*9)
BU7232SF(*9)
BU7251/BU7231
100
100
BU7252FVM(*10)
BU7232FVM(*10)
θja2
BU7252F(*9)
BU7232F(*9)
θja2 < θja1
T j(max)
105
100
150
150
125
Tj(max)
150