Datasheet LT3080 (Analog Devices) - 14

LT3080
applicaTions inForMaTion
of the connections between the regulator and the load.
Table 2. MSE Package, 8-Lead MSOP
The data sheet specification for load regulation is Kelvin
COPPER AREA THERMAL RESISTANCE
sensed at the pins of the package. Negative side sensing
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
is a true Kelvin connection, with the bottom of the voltage 2500mm2 2500mm2 2500mm2 55°C/W setting resistor returned to the negative side of the load 1000mm2 2500mm2 2500mm2 57°C/W (see Figure 7). Connected as shown, system load regula- 225mm2 2500mm2 2500mm2 60°C/W tion will be the sum of the LT3080 load regulation and the 100mm2 2500mm2 2500mm2 65°C/W parasitic line resistance multiplied by the output current. *Device is mounted on topside It is important to keep the positive connection between
Table 3. DD Package, 8-Lead DFN
the regulator and load as short as possible and use large
COPPER AREA
wire or PC board traces.
THERMAL RESISTANCE TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT) Thermal Considerations
2500mm2 2500mm2 2500mm2 60°C/W 1000mm2 2500mm2 2500mm2 62°C/W The LT3080 has internal power and thermal limiting cir- 225mm2 2500mm2 2500mm2 65°C/W cuitry designed to protect it under overload conditions. 100mm2 2500mm2 2500mm2 68°C/W For continuous normal load conditions, maximum junc- *Device is mounted on topside tion temperature must not be exceeded. It is important to give consideration to all sources of thermal resistance
Table 4. ST Package, 3-Lead SOT-223
from junction to ambient. This includes junction-to-case,
COPPER AREA THERMAL RESISTANCE
case-to-heat sink interface, heat sink resistance or circuit
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
board-to-ambient as the application dictates. Additional 2500mm2 2500mm2 2500mm2 48°C/W heat sources nearby must also be considered. 1000mm2 2500mm2 2500mm2 48°C/W For surface mount devices, heat sinking is accomplished 225mm2 2500mm2 2500mm2 56°C/W by using the heat spreading capabilities of the PC board 100mm2 2500mm2 2500mm2 62°C/W and its copper traces. Surface mount heat sinks and plated *Device is mounted on topside through-holes can also be used to spread the heat gener-
Table 5. Q Package, 5-Lead DD-Pak
ated by power devices.
COPPER AREA THERMAL RESISTANCE
Junction-to-case thermal resistance is specified from the
TOPSIDE* BACKSIDE BOARD AREA (JUNCTION-TO-AMBIENT)
IC junction to the bottom of the case directly below the 2500mm2 2500mm2 2500mm2 25°C/W die. This is the lowest resistance path for heat flow. Proper 1000mm2 2500mm2 2500mm2 30°C/W mounting is required to ensure the best possible thermal 125mm2 2500mm2 2500mm2 35°C/W flow from this area of the package to the heat sinking *Device is mounted on topside material. For the TO-220 package, thermal compound is
T Package, 5-Lead TO-220
strongly recommended for mechanical connections to a heat sink. A thermally conductive spacer can be used for Thermal Resistance (Junction-to-Case) = 3°C/W electrical isolation as long as the added contribution to thermal resistance is considered.
Note that the Tab or Calculating Junction Temperature Exposed Pad (depending on package) is electrically
Example: Given an output voltage of 0.9V, a VCONTROL
connected to the output.
voltage of 3.3V ±10%, an IN voltage of 1.5V ±5%, output The following tables list thermal resistance for several current range from 1mA to 1A and a maximum ambient different copper areas given a fixed board size. All mea- temperature of 50°C, what will the maximum junction surements were taken in still air on two-sided 1/16” FR-4 temperature be for the DFN package on a 2500mm2 board board with one ounce copper. with topside copper area of 500mm2? 3080fc 14 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Applications Information Typical Applications Package Description Revision History Typical Application Related Parts