Technical Note

BA00DD0WCP-V5,BA00DD0WHFP,BA00DD0WT,

BA00CC0WT,BA00CC0WT-V5,BA00CC0WCP-V5,BA00CC0WFP

6/9

www.rohm.com

2011.03 - Rev.C

© 2011 ROHM Co., Ltd. All rights reserved.

●

Thermal Design

HRP5

To225FP-5

TO252-5

Fig.30

Fig.31

Fig.32

When using at temperatures over Ta=25℃, please refer to the heat reducing characteristics shown in Fig.30 through 32.

The IC characteristics are closely related to the temperature at which the IC is used, so it is necessary to operate the IC at

Fig.31 shows the acceptable loss and heat reducing characteristics of the TO220FP package The portion shown by the

diagonal line is the acceptable loss range that can be used with the IC alone. Even when the ambient temperature Ta is a

normal temperature (25℃), the chip (junction) temperature Tj may be quite high so please operate the IC at temperatures

less than the acceptable loss Pd.

The calculation method for power consumption Pc(W) is as follows :

Pc = (Vcc-Vo)×Io＋Vcc×Icca

Acceptable loss Pd≦Pc

Solving this for load current IO in order to operate within the acceptable loss,

Io≦

（

Please refer to Figs.8 and 20 for Icca.）

Calculation Example

Example 1) When Ta=85℃, Vcc=8.3V, Vo=3.3V, BA33DD0WT

Io≦

With the IC alone : θja=62.5℃/W → -16mW/℃

Io≦200mA (Icca : 2mA)

25℃=2000mW → 85℃=1040mW

Please refer to the above information and keep thermal designs within the scope of acceptable loss for all operating

temperature ranges. The power consumption Pc of the IC when there is a short circuit (short between Vo and GND) is :

Pc=Vcc×(Icca＋Ishort)

Ishort : Short circuit current

●

Terminal Vicinity Settings and Cautions

・

Vcc Terminal

Please attach a capacitor (greater than 0.33μF) between the Vcc and GND.

The capacitance values differ depending on the application, so please chose a capacitor with sufficient margin and verify

the operation on an actual board.

・

CTL Terminal

The CTL terminal is turned ON at 2.0V and higher and OFF at 0.8V and lower within the operating power supply voltage range.

The power supply and the CTL terminal may be started up and shut down in any order without problems.

Pd – Vcc×Icca

Vcc－Vo

1.04－8.3×Icca

5

0.0

0.4

0.8

1.2

1.6

2.0

0

25

50

75

100

125

150

Ambient temperature:Ta(℃）

0

1

2

3

4

5

6

7

8

9

10

0

25

50

75

100

125

150

Ambient temperature:Ta(℃）

0

5

10

15

20

25

0

25

50

75

100

125

150

Ambient temperature:Ta(℃）

③

7.3W

②

5.5W

①

2.3W

（

1）20.0

（

2）2.0

1.30

①

②

③

（

1）

When using a maximum heat sick : θj-c=6.25(℃/W)

（

2）

When using an IC alone : θj-c=62.5(℃/W)

Mounted on a Rohm standard board

Board size : 70×70×1.6 ㎜

Copper foil area :7×7 ㎜

TO252-5θja=96.2(℃/W)

Vcc：

Vo：

Io：

Icca：

Input voltage

Output voltage

Load current

Circuit current