BU7242YFVM-C Datasheet, PDF (18/26 Pages) Rohm – Input/Output Full Swing Low Supply Current CMOS Operational Amplifier

BU7242YFVM-C
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 45(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 45(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 45(c) shows an example of the derating curve for BU7242YFVM-C.
Power Dissipation of LSI [W]
PDmax
θJA=(Tjmax-TA) / PD C/W
P2
θJA2 < θJA1
Ambient Temperature TA [ °C ]
θJA2
P1
Chip Surface Temperature TJ [ °C ]
(a) Thermal Resistance
θJA1
Tjmax
0
25
50
75
100 125 150
Ambient Temperature TA [ °C ]
(b) Derating Curve
0.8
0.6
(Note 9)
0.4
0.2
0.0
0
50
100
125
150
Ambient Temperature [°C]
(c)BU7242YFVM-C
(Note 9)
4.7
Unit
mW/°C
When using the unit above TA=25°C, subtract the value above per Celsius degree. Power dissipation is the value
when FR4 glass epoxy board 70mm×70mm×1.6mm (copper foil area less than 3%) is mounted
Figure 45. Thermal Resistance and Derating Curve
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