bd4912 ROHM Co. Ltd., bd4912 Datasheet - Page 11

• Manufacturer Part Number: bd4912
• Description: Dmos System Power Supply Ics With Low Current Consumption Now Available
• Manufacturer: ROHM Co. Ltd.

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.
Thermal design
P
• Power consumed by V
• 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
MAX
= P
The maximum power consumption P
maximum V
I
I
I
I
I
I
I
1
2
3
4
5
6
7
1
= Max. ILM output current
= Max. V
= Max. AUDIO output current
= Max. P.CON output current
= Max. P.ANT output current
= Max. AM output current
= Max. SW5V output current
+ P
2
+ P
DD
CC
3
+ P
1 input voltage and B denotes the maximum V
output current
50
30
20
10
40
4
0
+ P
DD
19.0(2)
8.0(3)
3.4(4)
Vref
37.5(1)
5
+ P
Fig.46 Power Dissipation Characteristics
25
6
+ P
7
+ P
AMBIENT TEMPERATURE:Ta〔℃〕
50
MAX
8
(W) can be calculated as described below, where A denotes the
Fig.47
11/16
75
P8 = A × Circuit current (circuit current is approximately 2 mA)
P1 = (B-5.0 V) × I
P2 = (A-8.12 V) × I
P3 = 0.7 V × I
P4 = 0.7 V × I
P5 = (A-7.9 V) × I
P6 = 0.7 V × I
P7 = (A-10.3 V) × I
100
3
4
6
Vcc
125
CC
Load
1
5
2 input voltage:
2
7
150
(1) When using an infinite heat sink θj-c = 2.0
(2) 100 × 100 × 2 (mm
(3) 50 × 50 × 2 (mm
(4) IC without heat sink operation.θj-a = 36.8 (°C /W)
(°C/W)
heat sink)
sink)
Note: When using an aluminum heat sink, use a
tightening torque of 6 (Kg
silicon grease.
3
) (when using an aluminum heat
3
) (when using an aluminum
•
cm) and apply