參數(shù)資料
型號(hào)： LMS8117ADT-3.3
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 基準(zhǔn)電壓源/電流源
英文描述： 1A Low-Dropout Linear Regulator
中文描述： 3.3 V FIXED POSITIVE LDO REGULATOR, 1.25 V DROPOUT, PSSO2
封裝： TO-252, 3 PIN
文件頁(yè)數(shù)： 9/16頁(yè)
文件大?。?/td> 777K
代理商： LMS8117ADT-3.3
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
相關(guān)PDF資料
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參數(shù)描述
LMS8117ADTADJ 制造商:Texas Instruments 功能描述:
LMS8117ADT-ADJ 功能描述:低壓差穩(wěn)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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20
LMS8117ADT-ADJ/NOPB 功能描述:低壓差穩(wěn)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(dòng)電壓（最大值）:307 mV 輸出電流:1 A 負(fù)載調(diào)節(jié):0.3 % 輸出端數(shù)量: 輸出類型:Fixed 最大工作溫度:+ 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:VQFN-20
LMS8117ADT-ADJ/NOPB 制造商:Texas Instruments 功能描述:Linear Voltage Regulator IC
LMS8117ADTX-1.8 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1A Low-Dropout Linear Regulator
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