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參數(shù)資料
| 型號： | LM1117 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 800mA Low-Dropout Linear Regulator(800mA低壓差線性穩(wěn)壓器) |
| 中文描述： | 800mA的低壓差線性穩(wěn)壓器（800mA的低壓差線性穩(wěn)壓器） |
| 文件頁數(shù)： | 11/19頁 |
| 文件大?。?/td> | 408K |
| 代理商： | LM1117 |
APPLICATION NOTE
(Continued)
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
R
(max):
T
R
(max)=T
J
(max)-T
A
(max)
where T
(max) is the maximum allowable junction tempera-
ture (125C), and T
(max) is the maximum ambient tem-
perature which will be encountered in the application.
Using the calculated values for T
(max) and P
, the maxi-
mum allowable value for the junction-to-ambient thermal
resistance (
θ
JA
) can be calculated:
θ
JA
= T
R
(max)/P
D
If the maximum allowable value for
θ
is found to be
≥
136C/W for SOT-223 package or
≥
79C/W for TO-220
package or
≥
92C/W for TO-252 package, no heatsink is
needed since the package alone will dissipate enough heat
to satisfy these requirements. If the calculated value for
θ
JA
falls below these limits, a heatsink is required.
As a design aid, Table 1 shows the value of the
θ
JA
of
SOT-223 and TO-252 for different heatsink area. The copper
patterns that we used to measure these
θ
JA
s are shown at
the end of theApplication Notes Section. Figure 7and Figure
8 reflects the same test results as what are in the Table 1
Figure 9and Figure 10shows the maximum allowable power
dissipation vs. ambient temperature for the SOT-223 and
TO-252 device. Figures Figure 11 and Figure 12 shows the
maximum allowable power dissipation vs. copper area (in
2
)
for the SOT-223 and TO-252 devices. Please see AN1028
for power enhancement techniques to be used with SOT-223
and TO-252 packages.
TABLE 1.
θ
JA
Different Heatsink Area
Layout
Copper Area
Thermal Resistance
Top Side (in
2
)*
0.0123
0.066
0.3
0.53
0.76
1
0
0
0
0
0
0.066
0.175
0.284
0.392
0.5
Bottom Side (in
2
)
0
0
0
0
0
0
0.2
0.4
0.6
0.8
1
0.066
0.175
0.284
0.392
0.5
(
θ
JA
,C/W) SOT-223
136
123
84
75
69
66
115
98
89
82
79
125
93
83
75
70
(
θ
JA
,C/W) TO-252
103
87
60
54
52
47
84
70
63
57
57
89
72
61
55
53
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
*Tab of device attached to topside copper
L
www.national.com
11
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相關代理商/技術參數(shù) |
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| LM1117_O6 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:800mA Low-Dropout Linear Regulator |
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