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參數資料
| 型號： | LMS8117ADTX-1.8 |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 基準電壓源/電流源 |
| 英文描述： | 1A Low-Dropout Linear Regulator |
| 中文描述： | 1.8 V FIXED POSITIVE LDO REGULATOR, 1.25 V DROPOUT, PSSO2 |
| 封裝： | TO-252, 3 PIN |
| 文件頁數： | 9/16頁 |
| 文件大小： | 777K |
| 代理商： | LMS8117ADTX-1.8 |
Application Note
(Continued)
The LMS8117Aregulators have internal thermal shutdown to
protect the device from over-heating. Under all possible
operating conditions, the junction temperature of the
LMS8117A must be within the range of 0C to 125C. A
heatsink may be required depending on the maximum power
dissipation and maximum ambient temperature of the appli-
cation. To determine if a heatsink is needed, the power
dissipated by the regulator, P
D
, must be calculated:
I
IN
= I
L
+ I
G
P
D
= (V
IN
-V
OUT
)I
L
+ V
IN
I
G
Figure 6
shows the voltages and currents which are present
in the circuit.
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
J
(max) is the maximum allowable junction tempera-
ture (125C), and T
A
(max) is the maximum ambient tem-
perature which will be encountered in the application.
Using the calculated values for T
R
(max) and P
D
, 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
≥
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
of
SOT-223 and TO-252 for different heatsink area. The copper
patterns that we used to measure these
θ
s are shown at
the end of theApplication Notes Section.
Figure 7
and
Figure
8
reflects the same test results as what are in the
Table 1
.
Figure 9
and
Figure 10
shows the maximum allowable power
dissipation vs. ambient temperature for the SOT-223 and
TO-252 device.
Figure 11
and
Figure 12
shows the maxi-
mum allowable power dissipation vs. copper area (in
2
) for
the SOT-223 and TO-252 devices. Please see AN–1028 for
power enhancement techniques to be used with SOT-223
and TO-252 packages.
10119637
FIGURE 5. Cross-sectional view of Integrated Circuit Mounted on a printed circuit board. Note that the case
temperature is measured at the point where the leads contact with the mounting pad surface
10119616
FIGURE 6. Power Dissipation Diagram
L
www.national.com
9
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMS8117ADTX-3.3 | 功能描述:低壓差穩壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節:0.3 % 輸出端數量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| LMS8117ADTX-3.3/NOPB | 功能描述:低壓差穩壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節:0.3 % 輸出端數量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| LMS8117ADTX-ADJ | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1A Low-Dropout Linear Regulator |
| LMS8117ADTX-ADJ/NOPB | 功能描述:低壓差穩壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節:0.3 % 輸出端數量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
| LMS8117AMP-1.8 | 功能描述:低壓差穩壓器 - LDO RoHS:否 制造商:Texas Instruments 最大輸入電壓:36 V 輸出電壓:1.4 V to 20.5 V 回動電壓（最大值）:307 mV 輸出電流:1 A 負載調節:0.3 % 輸出端數量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風格:SMD/SMT 封裝 / 箱體:VQFN-20 |
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