LT3080EDD LINER [Linear Technology], LT3080EDD Datasheet - Page 13

• Manufacturer Part Number: LT3080EDD
• Description: Adjustable1.1A Single Resistor Low Dropout Regulator
• Manufacturer: LINER [Linear Technology]

of the connections between the regulator and the load.
The data sheet specifi cation for load regulation is Kelvin
sensed at the pins of the package. Negative side sensing
is a true Kelvin connection, with the bottom of the voltage
setting resistor returned to the negative side of the load
(see Figure 7). Connected as shown, system load regula-
tion will be the sum of the LT3080 load regulation and the
parasitic line resistance multiplied by the output current.
It is important to keep the positive connection between
the regulator and load as short as possible and use large
wire or PC board traces.
Thermal Considerations
The LT3080 has internal power and thermal limiting cir-
cuitry designed to protect it under overload conditions.
For continuous normal load conditions, maximum junc-
tion temperature must not be exceeded. It is important
to give consideration to all sources of thermal resistance
from junction to ambient. This includes junction-to-case,
case-to-heat sink interface, heat sink resistance or circuit
board-to-ambient as the application dictates. Additional
heat sources nearby must also be considered.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Surface mount heat sinks and plated
through-holes can also be used to spread the heat gener-
ated by power devices.
Junction-to-case thermal resistance is specifi ed from the
IC junction to the bottom of the case directly below the
die. This is the lowest resistance path for heat fl ow. Proper
mounting is required to ensure the best possible thermal
fl ow from this area of the package to the heat sinking
material. For the TO-220 package, thermal compound is
strongly recommended for mechanical connections to a
heat sink. A thermally conductive spacer can be used for
electrical isolation as long as the added contribution to
thermal resistance is considered. Note that the Tab or
Exposed Pad (depending on package) is electrically
connected to the output.
The following tables list thermal resistance for several
different copper areas given a fi xed board size. All mea-
surements were taken in still air on two-sided 1/16” FR-4
board with one ounce copper.
APPLICATIONS INFORMATION
Table 2. MSE Package, 8-Lead MSOP
*Device is mounted on topside
Table 3. DD Package, 8-Lead DFN
Table 4. ST Package, 3-Lead SOT-223
*Device is mounted on topside
Table 5. Q Package, 5-Lead DD-Pak
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 3°C/W
Calculating Junction Temperature
Example: Given an output voltage of 0.9V, a V
voltage of 3.3V ±10%, an IN voltage of 1.5V ±5%, output
current range from 1mA to 1A and a maximum ambient
temperature of 50°C, what will the maximum junction
temperature be for the DFN package on a 2500mm
with topside copper area of 500mm
*Device is mounted on topside
*Device is mounted on topside
TOPSIDE*
TOPSIDE*
TOPSIDE*
TOPSIDE*
2500mm
1000mm
2500mm
1000mm
2500mm
1000mm
2500mm
1000mm
225mm
100mm
225mm
100mm
225mm
100mm
125mm
COPPER AREA
COPPER AREA
COPPER AREA
COPPER AREA
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
BACKSIDE
BACKSIDE
BACKSIDE
BACKSIDE
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
BOARD AREA
BOARD AREA
BOARD AREA
BOARD AREA
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2500mm
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
(JUNCTION-TO-AMBIENT)
(JUNCTION-TO-AMBIENT)
(JUNCTION-TO-AMBIENT)
(JUNCTION-TO-AMBIENT)
2
THERMAL RESISTANCE
THERMAL RESISTANCE
THERMAL RESISTANCE
THERMAL RESISTANCE
?
55°C/W
57°C/W
60°C/W
65°C/W
60°C/W
62°C/W
65°C/W
68°C/W
48°C/W
48°C/W
56°C/W
62°C/W
25°C/W
30°C/W
35°C/W
LT3080
CONTROL
13
2
board
3080fb