bd00d0awhfp ROHM Co. Ltd., bd00d0awhfp Datasheet - Page 7

• Manufacturer Part Number: bd00d0awhfp
• Description: 2a Standard Variable Output Ldo Regulator
• Manufacturer: ROHM Co. Ltd.

●Thermal Design
BD00D0AWHFP
© 2011 ROHM Co., Ltd. All rights reserved.
www.rohm.com
When using at temperatures over Ta=25℃, please refer to the heat reducing characteristics shown in Fig.15. and Fig.16.
The IC characteristics are closely related to the temperature at which the IC is used, so it is necessary to operate the IC
at temperatures less than the maximum junction temperature Tjmax.
Fig.15 and Fig.16 shows the acceptable loss and heat reducing characteristics of the HRP5 package. 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 :(Fig.16③)
Solving this for load current Io in order to operate within the acceptable loss,
It is then possible to find the maximum load current Io
design.
Calculation Example)When Ta=85℃,Vcc=10V,Vo=5V
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－Vo)×Io+Vcc×Ib
Acceptable loss Pd≧Pc
Pc=Vcc×(Ib+Ishort)
10
8
6
4
2
0
Io≦
Io≦
Io≦758.2mA (Ib:0.5mA)
0
1.6W
25
Pd－Vcc×Ib
3.796－10×Ib
Mounted on a Rohm standard board
Board size : 70 ㎜× 70 ㎜× 1.6 ㎜
θ ja=78.1( ℃ /W)
Vcc－Vo
Temperature atmosphere Ta(℃)
50
5
Fig.15
75
100
(Please refer to Fig. 5 for Ishort)
125
(Please refer to Fig.9 for Ib.)
150
Fig.16③:θja=17.1℃/W → -58.4mW/℃
25℃=7.3W → 85℃=3.796W
Max
7/11
with respect to the applied voltage Vcc at the time of thermal
10
8
6
4
2
0
0
③ 7.3W
② 5.5W
① 2.3W
25
Fig.16 (Reference data)
Temperature atmosphere Ta(℃)
Mounted on a Rohm standard board
Board size : 70 ㎜×70 ㎜×1.6 ㎜
①2-layer board
②2-layer board
③4-layer board
50
(back surface copper foil area :15 ㎜×15 ㎜)
(back surface copper foil area :70 ㎜×70 ㎜)
(back surface copper foil area :70 ㎜×70 ㎜)
(board contains a thermal)
75
①:θja=54.3℃/W
②:θja=22.7℃/W
③:θja=17.1℃/W
100
Ishort:
Vcc:
Vo:
Io:
Ib:
125
Technical Note
2011.03 - Rev.A
Input voltage
Output voltage
Load current
Circuit current
Short current
150