BU7294F Datasheet, PDF (22/30 Pages) Rohm – Input/Output Full Swing High Slew Rate Low Voltage CMOS Operational Amplifiers

BU7291G, BU7291SG, BU7294xx, BU7294Sxx
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 55. (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
・・・・・ (Ⅰ)
The Derating curve in Figure 55. (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 56. (c) to (d) shows an example of the derating curve for BU7291,
BU7291S, BU7294, BU7294S.
θja=(Tjmax-Ta)/Pd C/W
Ambient temperature Ta[ C ]
Power dissipation of LSI [W]
Pd(max)
P2
θja2 <θja1
P1
θja2
Tj(max)
θja1
Chip surface temperature Tj[ C ]
(a) Thermal resistance
0
25
50
75
100
125
Ambient temperature Ta[C]
(b) Derating curve
Figure 55. Thermal resistance and Derating Curve
1₁0_.000
1₁0_.000
0⁸.8⁰⁰
0⁶.6⁰⁰
0⁴.4⁰⁰
0².2⁰⁰
BU7294FV (*13)
BU7291G (*14)
BU7294F (*15)
0⁸.8⁰⁰
0⁶.6⁰⁰
0⁴.4⁰⁰
0².2⁰⁰
BU7294SFV (*13)
BU7294SF (*15)
BU7291SG (*14)
0
0
25
50
75 ⁸⁵ 100
AMBIENT TEMPERATURE [℃]
0
105
0
25
50
75
100
125
AMBIENT TEMPERATURE [℃]
(*13)
(*14)
(*15)
Unit
7.0
5.4
4.5
mW/C
When using the unit above Ta=25C, subtract the value above per degree C. Power dissipation is the value
when FR4 glass epoxy board 70mm×70mm×1.6mm (cooper foil area below 3%) is mounted
Figure 56. Derating Curve
www.rohm.com
©2013 ROHM Co., Ltd. All rights reserved.
TSZ22111ï½¥15ï½¥001
22/27
TSZ02201-0RAR1G200390-1-2
22.May.2013 Rev.001