BD4912 查看數據表（PDF） - ROHM Semiconductor

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BD4912

DMOS System Power Supply ICs with low current consumption

ROHM Semiconductor 

zThermal design

50

40

37.5(1)

30

20 19.0(2)

(1) When using an infinite heat sink θj-c = 2.0

(°C/W)

(2) 100 × 100 × 2 (mm3) (when using an aluminum

heat sink)

(3) 50 × 50 × 2 (mm3) (when using an aluminum heat

sink)

(4) IC without heat sink operation.θj-a = 36.8 (°C /W)

Note: When using an aluminum heat sink, use a

tightening torque of 6 (Kg • cm) and apply

silicon grease.

8.0(3)

10

3.4(4)

0

25

50

75

100

125

150

AMBIENT TEMPERATURE:Ta〔℃〕

Fig.46 Power Dissipation Characteristics

Refer to the heat reduction characteristics illustrated in Fig. 46 when using the IC in an environment where Ta ≥ 25°C. The

characteristics of the IC are greatly influenced by the operating temperature. If the temperature is in excess of the maximum

junction temperature Tjmax, the elements of the IC may be deteriorated or damaged. It is necessary to give sufficient

consideration to the heat of the IC in view of two points; First, the protection of the IC from instantaneous damage and second,

the maintenance of the reliability of the IC in long-time operation.

In order to protect the IC from thermal destruction, it is necessary to operate the IC below the maximum junction temperature

Tjmax. The chip's (junction area) temperature Tj may rise considerably even when the IC is being used at room temperature

(25°C). Always operate the IC within the power dissipation Pd.

Vcc

Vref

Load

Fig.47

The maximum power consumption PMAX (W) can be calculated as described below, where A denotes the

maximum VCC1 input voltage and B denotes the maximum VCC2 input voltage:

I1 = Max. VDD output current

I2 = Max. AUDIO output current

I3 = Max. P.CON output current

I4 = Max. P.ANT output current

I5 = Max. AM output current

I6 = Max. SW5V output current

I7 = Max. ILM output current

• Power consumed by VDD

• Power consumed by AUDIO

• Power consumed by P.CON

• Power consumed by P.ANT

• Power consumed by AM

• Power consumed by SW5V

• Power consumed by ILM

• Power consumed by each circuit's current

P1 = (B-5.0 V) × I1

P2 = (A-8.12 V) × I2

P3 = 0.7 V × I3

P4 = 0.7 V × I4

P5 = (A-7.9 V) × I5

P6 = 0.7 V × I6

P7 = (A-10.3 V) × I7

P8 = A × Circuit current (circuit current is approximately 2 mA)

PMAX = P1 + P2 + P3 + P4 + P5 + P6 + P7 + P8

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