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參數(shù)資料
| 型號： | LM1084 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 5A Low Dropout Positive Regulators |
| 中文描述： | 第5A低壓差穩(wěn)壓器正 |
| 文件頁數(shù)： | 9/13頁 |
| 文件大?。?/td> | 750K |
| 代理商： | LM1084 |
Application Note
(Continued)
must be added, one for case to heat-sink (
θ
CH
) and one for
heatsink to ambient (
θ
HA
). The junction temperature can be
predicted as follows:
T
J
= T
A
+ P
D
(
θ
JC
+
θ
CH
+
θ
HA
) = T
A
+ P
D
θ
JA
T
J
is junction temperature, T
A
is ambient temperature, and
P
is the power consumption of the device. Device power
consumption is calculated as follows:
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.
Once the devices power is determined, the maximum allow-
able (
θ
JA (max)
) is calculated as:
θ
JA (max)
= T
R(max)
/P
D
= T
J(max)
T
A(max)
/P
D
The LM1084 has different temperature specifications for two
different sections of the IC: the control section and the output
section. The Electrical Characteristics table shows the junc-
tion to case thermal resistances for each of these sections,
while the maximum junction temperatures (T
) for each
section is listed in the Absolute Maximum section of the
datasheet. T
J(max)
is 125C for the control section, while
T
J(max)
is 150C for the output section.
θ
JA (max)
should be calculated separately for each section as
follows:
θ
JA
(max, CONTROL SECTION) = (125C - T
)/P
D
θ
JA
(max, OUTPUT SECTION) = (150C - T
A(max)
)/P
D
The required heat sink is determined by calculating its re-
quired thermal resistance (
θ
HA (max)
).
θ
HA (max)
=
θ
JA (max)
(
θ
JC
+
θ
CH
)
(
θ
HA (max)
) should also be calculated twice as follows:
(
θ
) =
θ
(max, CONTROL SECTION) - (
θ
JC
(CON-
TROL SECTION) +
θ
CH
)
(
θ
) =
θ
JA
(max, OUTPUT SECTION) - (
θ
JC
(OUTPUT
SECTION) +
θ
CH
)
If thermal compound is used,
θ
can be estimated at 0.2
C/W. If the case is soldered to the heat sink, then a
θ
CH
can
be estimated as 0 C/W.
After,
θ
HA (max)
is calculated for each section, choose the
lower of the two
θ
HA (max)
values to determine the appropri-
ate heat sink.
If PC board copper is going to be used as a heat sink, then
Figure 7
can be used to determine the appropriate area
(size) of copper foil required.
10094616
FIGURE 6. Power Dissipation Diagram
10094664
FIGURE 7. Heat sink thermal Resistance vs Area
L
www.national.com
9
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|---|---|
| LM1084S-3.3 | 5A LOW DROPOUT VOLTAGE REGULATOR (Adjustable & Fixed) |
| LM1085IS-12 | 3A Low Dropout Positive Regulators |
| LM1085IS-3.3 | 3A Low Dropout Positive Regulators |
| LM1085IS-5.0 | 3A Low Dropout Positive Regulators |
| LM1085IS-ADJ | 3A Low Dropout Positive Regulators |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM1084-15 | 制造商:TGS 制造商全稱:Tiger Electronic Co.,Ltd 功能描述:5A LOW DROPOUT POSITIVE REGULATOR |
| LM1084-18 | 制造商:TGS 制造商全稱:Tiger Electronic Co.,Ltd 功能描述:5A LOW DROPOUT POSITIVE REGULATOR |
| LM1084-25 | 制造商:TGS 制造商全稱:Tiger Electronic Co.,Ltd 功能描述:5A LOW DROPOUT POSITIVE REGULATOR |
| LM1084-33 | 制造商:TGS 制造商全稱:Tiger Electronic Co.,Ltd 功能描述:5A LOW DROPOUT POSITIVE REGULATOR |
| LM1084-50 | 制造商:TGS 制造商全稱:Tiger Electronic Co.,Ltd 功能描述:5A LOW DROPOUT POSITIVE REGULATOR |
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