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BAXXDD0W Datasheet(Fiches technique) 6 Page - Rohm

Numéro de pièce BAXXDD0W
Description  BAXXDD0_10
Télécharger  10 Pages
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Fabricant  ROHM [Rohm]
Site Internet  http://www.rohm.com
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Technical Note
BA□□DD0 Series,BA□□CC0 Series,
BA□□DD0W Series,BA□□CC0W Series
6/9
www.rohm.com
2010.02 - Rev.B
© 2010 ROHM Co., Ltd. All rights reserved.
Thermal Design
HRP-5
TO220FP-5
TO252-5
Fig.29
Fig.30
Fig.31
When using at temperatures over Ta=25℃, please refer to the heat reducing characteristics shown in Fig.29 through 31. The
IC characteristics are closely related to the temperature at which the IC is used and if the temperature exceeds the maximum
junction temperature TjMAX., the elements may be damaged or destroyed. From the standpoints of instantaneous destruction
and long-term operating reliability, it is necessary give sufficient consideration to IC heat. In order to protect the IC from
thermal damage, it is necessary to operate it at temperatures lower than the maximum junction temperature TjMAX of the IC.
Fig.30 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 method of calculating the 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.)
It is then possible to find the maximum load current IoMAX with respect to the applied voltage Vcc at the time of thermal design.
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
Peripheral Circuit Considerations
Vcc Terminal
Please attach a capacitor (greater than 0.33μF) between the Vcc and GND.
The capacitance values will differ depending on the application, so please take this into account when configuring the terminal.
GND Terminal
Please be sure to keep the set ground and IC ground at the same potential level so that a potential difference does not
arise between them.
If a potential difference arises between the set ground and the IC ground, the preset voltage will not be outputted, causing
the system to become unstable. Therefore, please reduce the impedance by making the ground patterns as wide as
possible and by reducing the distance between the set ground and the IC ground as much as possible.
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.
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(℃)
7.3W
5.5W
2.3W
1)20.0
2)2.0
1.30
Board size : 70×70×1.6 ㎜ 3 (board contains a thermal via)
Board front copper foil area : 10.5×10.5 ㎜ 2
2-layer board (back surface copper foil area :15×15 ㎜ 2)
2-layer board (back surface copper foil area :70×70 ㎜ 2)
4-layer board (back surface copper foil area :70×70 ㎜ 2)
1)
When using a maximum heat sick : θj-c=6.25(℃/W)
2)
When using an IC alone : θj-6=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)
Pd – Vcc×Icca
Vcc-Vo
1.04-8.3×Icca
5
Vcc:
Vo:
Io:
Vcca:
Input voltage
Output voltage
Load current
Circuit current




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