BD8381EFV-M 查看數據表（PDF） - ROHM Semiconductor

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BD8381EFV-M

LED Drivers for Automotive Light

ROHM Semiconductor 

BD8381EFV-M

●Power consumption calculation

Pc(N) = ICC*VCC +

1

2

*Ciss*VREG*Fsw*VREG×2×2+

1

2

×Ciss×VREG×FPWM×VREG×2

ICC ： Current of the maximum circuit

VCC ：Power-supply voltage

Ciss ： External FET capacity

Vsw ： SW gate voltage

Fsw ： SW frequency

FPWM ： PWM frequency

＜Calculation example＞

When assuming

Pc(4)

=

10mA

×

30V

+

500pF

×

5V

×

300kHz

×

5V×2×2+

1

2

×1500pF×5×200×5×2,

it becomes

Pc = about 300mW.

4

(3) 3.12W

3

(2) 2.77W

(1) θja=66.5℃/W (Density of board copper foil3%)

(2) θja=45℃/W (Density of board copper foil34%)

(3) θja=40℃/W (Density of board copper foil60%)

2

(1) 1.88W

1

Technical Note

0

25

50

75

95 100

125

150

Ambient temperature Ta[℃]

Fig.22

Note1: The value of Power consumption : on glass epoxy board measuring 70mm×70mm×1.6mm

(1 layer board/Copper foil thickness 18µm)

Note2: The value changes depending on the density of the board copper foil.

However, this value is an actual measurement value and no guarantee value.

Pd=2200mW (968mW) ： Density of the board copper foil 3%

Pd=3200mW (1408mW)： Density of the board copper foil 34%

Pd=3500mW (1540mW)： Density of the board copper foil 60% The value in () is a Power consumption of the Ta=125℃.

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2011.04 - Rev.A

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