BD3951F Просмотр технического описания (PDF) - ROHM Semiconductor

Номер в каталоге

Компоненты Описание

Список матч

BD3951F

Regulator with Voltage Detector IC

ROHM Semiconductor 

BD3951F

Technical Note

●Thermal Design

1000

800

687

600

Glass Epoxy Board (70mm×70mm×1.6mm)

Mount Condition Θj-a=181.8 (℃/W)

400

200

0

0

25

50

75

100 125 150

Ta

[ ℃]

Fig.17

Please consider about power dissipation de-rating curve for high temperature operations. IC characteristics receive great

effect from operating ambient temperature. If junction temperature exceeds rating temperature (Tjmax), device might

degrade or be demolished permanently. Heat design should take consideration from both instant demolish and long life

reliability.To prevent thermal destroy, IC must be operated under the condition that junction temperature is less than Tjmax.

SOP8 package power dissipation temperature de-rating curve is shown in Fig. 17. Operating condition must be less than

power dissipation curve. Calculation formula is as below.

Pc=(Vcc-VOUT)×IOUT+Vcc×Icc

Power Dissipation Pd ≤ Pc

Derive IOUT as operation is less than power dissipation curve,

IOUT ≤

Pd-Vcc×Icc

Vcc-VOUT

(Icc is shown in Fig. 1)

IOUT max is defined by Vcc and VOUT.

Vcc

:

VOUT :

IOUT :

Icc

:

Input Voltage

Output Voltage

Output Current

Circuit Current

·Example

Ta=85℃, Vcc=13.5V and VOUT=5V

IOUT ≤

0.357-13.5×Icc

13.5-5

IOUT≤41.8mA (Icc=135μA)

θja=181.8℃/W→-5.5mW/℃

25℃=687mW→85℃=357mW

Power consumption (Pc) has to be less than power dissipation curve along with the temperature.

The equation under short circuit condition (VOUT-GND short) is as below.

Pc=Vcc×(Icc+Ishort) Ishort=Short Current

www.rohm.com

6/9

© 2009 ROHM Co., Ltd. All rights reserved.

2009.07 - Rev.A

Share Link: