BU7241G_14 Datasheet, PDF (32/48 Pages) Rohm – CMOS Operational Amplifiers

BU7241G BU7241SG BU7242xxx BU7242Sxxx BU7244xx BU7244Sxx ^Datasheet
Power Dissipation
Power dissipation (total loss) indicates the power that the IC can consume at TA=25°C (normal temperature). As the IC
consumes power, it heats up, causing its temperature to be higher than the ambient temperature. The allowable
temperature that the IC can accept is limited. This depends on the circuit configuration, manufacturing process, and
consumable power.
Power dissipation is determined by the allowable temperature within the IC (maximum junction temperature) and the
thermal resistance of the package used (heat dissipation capability). Maximum junction temperature is typically equal to the
maximum storage temperature. The heat generated through the consumption of power by the IC radiates from the mold
resin or lead frame of the package. Thermal resistance, represented by the symbol θJA°C/W, indicates this heat dissipation
capability. Similarly, the temperature of an IC inside its package can be estimated by thermal resistance.
Figure 78(a) shows the model of the thermal resistance of a package. The equation below shows how to compute for the
Thermal resistance (θJA), given the ambient temperature (TA), maximum junction temperature (TJmax), and power dissipation
(PD).
θJA = (TJmax－TA) / PD °C/W
The Derating curve in Figure 78 (b) indicates the power that the IC can consume with reference to ambient temperature.
Power consumption of the IC begins to attenuate at certain temperatures. This gradient is determined by Thermal
resistance (θJA), which depends on the chip size, power consumption, package, ambient temperature, package condition,
wind velocity, etc. This may also vary even when the same of package is used. Thermal reduction curve indicates a
reference value measured at a specified condition. Figure 78(c) to 78(h) shows an example of the derating curve for
BU7241G, BU7241SG, BU7242xxx, BU7242Sxxx, BU7244xx, BU7244Sxx.
θJA=(TJmax-TA)/ PD °C/W
Ambient temperature TA [ °C ]
Chip surface temperature TJ [ °C ]
(a) Thermal resistance
Power dissipation of LSI [W]
PDmax
P2
θJA2 < θJA1
P1
θJA2
θJA1
TJmax
0
25
50
75
100
125
Ambient temperature TA[C]
(b) Derating Curve
0.8
0.8
0.6
BU7241G(Note 28)
0.4
0.6
BU7241SG(Note 28)
0.4
0.2
0.2
0.0
0
85
25
50
75 100 125
Ambient Temperature [°C]
(c)BU7241G
0.0
0
105
25
50
75 100 125
Ambient Temperature [°C]
(d)BU7241SG
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TSZ02201-0RAR0G200240-1-2
03.Dec.2014 Rev.003