BD3650FP-M Datasheet, PDF (6/11 Pages) Rohm – LDO Regulator

BD3650FP-M
●Thermal Dissipation Curve
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B基oa板rdサsiイzeズ：:7700mmmm××7700mmmm××11..66mmmm
foil銅ar箔ea面:7積m:m7m×m7m×m7mm
4
TOT2O52-532:Sθ_-3ja=1θ04ja.=2(1℃_{04/W.2()℃/W)}
3
2
1.20
1
Technical Note
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③ 4.80
4
② 3.50
3
2 ^{① 1.85}
1
ROHM standard board
Board size:70mm×70mm×1.6mm
foil area:7mm×7mm
①2-layer board(back surface copper foil area:15mm×15mm)
②2-layer board(back surface copper foil area:70mm×70mm)
③4-layer board(back surface copper foil area:70mm×70mm)
①θja=67.6(℃/W)
②θja=35.7(℃/W)
③θja=26.0(℃/W
0
0
25
50
75
100
125
150
Ambient Temperature: Ta(℃)
Fig.11
0
0
25
50
75
100
125
150
Ambient Temperature: Ta(℃)
Fig.12
(Reference Data)
When using at temperatures over Ta=25℃, please refer to the heat reducing characteristics shown in Fig.11 and Fig.12.
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.11 and Fig.12 shows the acceptable loss and heat reducing characteristics of the TO252-3 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.12③)
Pc=(Vcc－Vo)×Io+Vcc×Ib
Acceptable loss Pd≧Pc
Solving this for load current Io in order to operate within the acceptable loss,
IO
≦
Pd  VCC Ib
VCC  VO
(Please refer to Figs.8 for Ib.)
It is then possible to find the maximum load current I_OMAX with respect to the
applied voltage Vcc at the time of thermal design.
V_CC: Input voltage
Vo: Output voltage
Io: Load current
Ib: Circuit current
Ishort: Short current
Calculation Example)
When Ta=85℃, Vcc=10V, Vo=5V
IO
≦
2.469

5
10

Ib
IO≦300mA (Ib:0.5mA)
Fig.12③:θja=26.0℃/W → -38.4mW/℃
25℃=4.80W → 85℃=2.496W
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=V_CC×(Ib+Ishort)
(Please refer to Fig.4 for Ishort.)
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6/10
2010.11 - Rev.A