BU7233F datasheet(18/27 Pages) ROHM

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Datasheet

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TSZ02201-0RFR1G200440-1-2

18/24

25.Dec.2013 Rev.002

TSZ22111･15･001

BU7230G

BU7230SG

BU7233F

BU7233SF

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 44(a) shows the model of the thermal resistance of the 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 44(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 44(c) to (f) shows the derating curve for BU7230G, BU7230SG,

BU7233F and BU7233SF.

0.0

0.2

0.4

0.6

0.8

100

125

Ambient Temperature [°C]

0.0

0.2

0.4

0.6

0.8

100

125

Ambient Temperature [°C]

BU7230G

(Note 12)

BU7230SG

(Note 12)

(d) BU7230SG

105

(b) Derating Curve

Ambient Temperature TA[

C ]

Chip Surface Temperature TJ [C]

(a) Thermal Resistance

θJA=(TJmax-TA)/PD C/W

Ambient Temperature

TA[C]

125

100

Power Dissipation of LSI [W]

PDmax

TJmax

JA2

JA1

JA2 <θJA1

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