LM1084IT-5.0 National Semiconductor, LM1084IT-5.0 Datasheet - Page 9

• Manufacturer Part Number: LM1084IT-5.0
• Description: V REG LDO 5A +5.0V, 1084, TO-220-3
• Manufacturer: National Semiconductor

Specifications of LM1084IT-5.0

• Output Voltage: 5V
• Dropout Voltage Vdo: 1.3V
• No. Of Pins: 3
• Voltage Regulator Case Style: TO-220
• Operating Temperature Range: -40°C To +125°C
• Svhc: No SVHC (15-Dec-2010)
• Operating Temperature: RoHS Compliant

APPLICATION NOTE
T
P
consumption is calculated as follows:
Once the devices power is determined, the maximum allow-
able (θ
θ
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
section is listed in the Absolute Maximum section of the
datasheet. T
T
θ
follows:
θ
θ
The required heat sink is determined by calculating its re-
quired thermal resistance (θ
JA (max)
JA (max)
JA
JA
J
J(max)
D
is junction temperature, T
is the power consumption of the device. Device power
(max, CONTROL SECTION) = (125˚C - T
(max, OUTPUT SECTION) = (150˚C - T
JA (max)
is 150˚C for the output section.
should be calculated separately for each section as
= T
R(max)
J(max)
) is calculated as:
/P
is 125˚C for the control section, while
D
= T
J(max)
HA (max)
A
is ambient temperature, and
− T
).
A(max)
(Continued)
FIGURE 7. Heat sink thermal Resistance vs Area
/P
FIGURE 6. Power Dissipation Diagram
D
A(max)
J(max)
A(max)
) for each
)/P
10094616
)/P
D
D
9
Figure 6 shows the voltages and currents which are present
in the circuit.
θ
(θ
(θ
TROL SECTION) + θ
(θ
SECTION) + θ
If thermal compound is used, θ
C/W. If the case is soldered to the heat sink, then a θ
be estimated as 0 C/W.
After, θ
lower of the two θ
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.
HA (max)
HA (max)
HA (max)
HA (max)
I
P
IN
D
HA (max)
= I
= (V
) should also be calculated twice as follows:
) = θ
= θ
) = θ
L
10094664
+ I
IN
JA (max)
JA
−V
JA
CH
G
(max, OUTPUT SECTION) - (θ
is calculated for each section, choose the
OUT
)
(max, CONTROL SECTION) - (θ
HA (max)
) I
− (θ
CH
L
)
+ V
JC
values to determine the appropri-
+ θ
IN
I
G
CH
CH
)
can be estimated at 0.2
JC
www.national.com
(OUTPUT
JC
CH
(CON-
can