LT1084CT-12 Linear Technology, LT1084CT-12 Datasheet - Page 9

• Manufacturer Part Number: LT1084CT-12
• Description: IC LDO REG 5A 12V TO-220-3
• Manufacturer: Linear Technology

Specifications of LT1084CT-12

• Regulator Topology: Positive Fixed
• Voltage - Output: 12V
• Voltage - Input: Up to 25V
• Voltage - Dropout (typical): 1.3V @ 5A
• Number Of Regulators: 1
• Current - Output: 5A
• Current - Limit (min): 5.5A
• Operating Temperature: 0°C ~ 150°C
• Mounting Type: Through Hole
• Package / Case: TO-220-3 (Straight Leads)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

INPUT
APPLICATIO S I FOR ATIO
case- to-heat sink interface, and heat sink resistance itself.
New thermal resistance specifications have been devel-
oped to more accurately reflect device temperature and
ensure safe operating temperatures. The data section for
these new regulators provides a separate thermal resis-
tance and maximum junction temperature for both the
Control Section and the Power Section . Previous regula-
tors, with a single junction-to-case thermal resistance
specification, used an average of the two values provided
here and therefore could allow excessive junction tem-
peratures under certain conditions of ambient tempera-
ture and heat sink resistance. To avoid this possibility,
calculations should be made for both sections to ensure
that both thermal limits are met.
Junction-to-case thermal resistance is specified from the
IC junction to the bottom of the case directly below the die.
This is the lowest resistance path for heat flow. Proper
mounting is required to ensure the best possible thermal
flow from this area of the package to the heat sink. Thermal
compound at the case-to-heat sink interface is strongly
recommended. If the case of the device must be electroni-
cally isolated, a thermally conductive spacer can be used
as long as its added contribution to thermal resistance is
considered. Note that the case of all devices in this series
is electronically connected to the ouput.
TYPICAL APPLICATIO S
28V
10k
1k
U
1M
LT1011
High Efficiency Regulator
MR1122
+
–
U
1mH
10,000μF
1N914
+
28V
U
4N28
W
10k
10k
470Ω
1N914
28V
IN
U
LT1083-5 OUT
GND
LT1083/4/5 TA03
For example, using a LT1083-5CP (TO-3P, Commercial)
and assuming:
Power dissipation under these conditions is equal to:
Junction temperature will be equal to:
For the Control Section:
For the Power Transistor:
In both cases the junction temperature is below the
maximum rating for the respective sections, ensuring
reliable operation.
OUTPUT
V
T
θ
thermal compound.
P
T
T
118°C
118°C < 125°C = T
cial Range)
T
142°C
142°C < 150°C = T
cial Range)
A
J
J
J
CASE-TO-HEAT SINK
IN
D
LT1083/LT1084/LT1085 Fixed
= T
= 75°C + 24W (1°C/W + 0.2°C/W + 0.5°C/W) =
= 75°C + 24W (1°C/W + 0.2°C/W + 1.6°C/W) =
= 75°C, θ
(max continuous) = 9V, V
= (V
A
IN
+ P
V
– V
IN
D
HEAT SINK
(θ
OUT
HEAT SINK
IN
IN
) (I
JMAX
JMAX
= 0.2°C/W for P package with
LT1083-5 OUT
LT1083-5
OUT
GND
GND
Paralleling Regulators
= 1°C/W,
) = 24W
(Control Section Commer-
(Power Transistor Commer-
+ θ
OUT
CASE-TO-HEAT SINK
OUT
= 5V, I
LT1083/4/5 TA04
*THE #18 WIRE ACTS
0.015Ω
AS BALLAST RESISTANCE
INSURING CURRENT SHARING
BETWEEN BOTH DEVICES
2 FEET #18 WIRE*
OUT
V
I
OUT
= 6A,
OUT
+ θ
= 0A TO 15A
= 5V
JC
1083ffd
9
)