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TSZ02201-0J2J0A900980-1-2

© 2015 ROHM Co., Ltd. All rights reserved.

02.Nov.2015 Rev.001

www.rohm.com

TSZ22111・15・001

BD3538F

BD3538HFN

2.

Power Dissipation

Heat Loss

In thermal design, consider the temperature range wherein the IC is guaranteed to operate and apply appropriate

margins. The temperature conditions that need to be considered are listed below:

(1) Ambient temperature Ta: 100°C or lower

(2) Chip junction temperature Tj: 150°C or lower

The chip junction temperature Tj can be considered as follows. See below diagrams

for θja.

Since the package has FIN at the bottoms of IC, package power is considerably affected by the area of the copper foil

where FIN is connected. In order to release heat, please make the board area large enough or add many

through-holes to the inner layer pattern. Most of heat loss in BD3538 occurs at the output N-channel FET. The power

lost is determined by multiplying the voltage between IN and OUT by the output current. Since this IC is packaged for a

high power applications. its thermal derating characteristics significantly depend on the PC board. So when designing,

the size of the PC board to be used should be carefully considered.

 













 

Ave

I

V

V

voltage

Output

V

voltage

Input

W

n

dissipatio

Power

OUT

VDDQ

VTT

IN

VTT









2

1

_

 

 

 





 

 

W

4

.

0

A

5

.

0

V

9

.

0

V

8

.

1

W

n

dissipatio

Power









◎SOP8

◎HSON8

(1) 70mm x 70mm x 1.6mm Glass-epoxy PCB

θj-c=181°C/W

(2) With no heat sink

θj-a=222°C/W

0.0

0.5

1.0

1.5

2.0

0

25

50

75

100

125

150

Ambient Temperature：Ta(℃)

(3) 0.63W

(2) 1.35W

(1) 1.75W

(1) 1 layer (copper foil density : 65%）

θja=71.4°C/W

(2) 1 layer (copper foil density : 7%)

θja=92.4°C/W

(3) 1 layer (copper foil density : 0.2%)

θja=198.4°C/W

Ambient Temperature : Ta (°C)

0

100

200

300

400

500

600

700

800

0

25

50

75

100

125

150

Ambient Temperature：Ta(℃)

(2) 0.56W

(1) 0.69W

100°C

Ambient Temperature : Ta (°C)

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1