○Product structure：Silicon monolithic integrated circuit ○This product is not designed protection against radioactive rays

8/12

TSZ02201-0H1H0B100490-1-2

© 2012 ROHM Co., Ltd. All rights reserved.

18.DEC.2012 Rev.002

TSZ22111・14・001

BA6506F

www.rohm.com

●Thermal derating curve

Power dissipation (total loss) indicates the power that can be consumed by IC at Ta = 25ºC (normal temperature). IC is

heated when it consumes power, and the temperature of IC chip becomes higher than ambient temperature. The

temperature that can be accepted by IC chip depends on circuit configuration, manufacturing process, etc, 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 in general equal to

the maximum value in the storage temperature range.

Heat generated by consumed power of IC is radiated from the mold resin or lead frame of package. The parameter which

indicates this heat dissipation capability (hardness of heat release) is called heat resistance, represented by the symbol

θja

[℃/W]. The temperature of IC inside the package can be estimated by this heat resistance. Fig.11 shows the model of heat

resistance of the package.

Heat resistance

θja, ambient temperature Ta, junction temperature Tj, and power consumption P can be calculated by the

equation below:

θja ＝ (Tj−Ta) / P

[℃/W]

Thermal derating curve 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, packaging condition,

wind velocity, etc., even when the same package is used. Thermal derating curve indicates a reference value measured at

a specified condition. Fig.12 shows a thermal derating curve (Value when mounting FR4 glass epoxy board 70 [mm] x 70

[mm] x 1.6 [mm] (copper foil area below 3 [%]))

●Equivalent circuit

1) Hall input terminal

2) Output terminal

3)FG signal output terminal

Pd(mW)

700

600

500

400

300

200

100

025

50

75

100

125

150

Ta(℃)

95

BA6506F

624

800

780

85

θja = (Tj-Ta) / P

[℃/W]

Fig.11 Thermal resistance

Ambient temperature Ta[℃]

Chip surface temperature Tj[℃]

Power

consumption

P[W]

H+

H-

1kΩ

1kΩ

Vcc

A1,A2

15kΩ

FG

＊

Reduce by 6.24 mW/°C over 25°C.

(70.0mm×70.0mm×1.6mm glass epoxy board)

Fig.12 Thermal derating curve