LT3030HFE-PBF 데이터 시트보기 (PDF) - Linear Technology
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LT3030HFE-PBF Datasheet PDF : 22 Pages
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LT3030
Applications Information
1. Output current multiplied by the input/output voltage
differential: (IOUT)(VIN – VOUT), and
2.GND pin current multiplied by the input voltage:
(IGND)(VIN).
Ground pin current is found by examining the GND Pin
Current curves in the Typical Performance Characteristics
section.
Table 3. FE Package, 20-Lead TSSOP
COPPER AREA
TOPSIDE*
2500mm2
1000mm2
225mm2
100mm2
BACKSIDE
2500mm2
2500mm2
2500mm2
2500mm2
BOARD AREA
2500mm2
2500mm2
2500mm2
2500mm2
*Device is mounted on topside.
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
25°C/W
27°C/W
28°C/W
32°C/W
Power dissipation for each channel equals the sum of the
two components listed above. Total power dissipation for
the LT3030 equals the sum of the power dissipated by
each channel.
The junction-to-case thermal resistance (θJC), measured
at the exposed pad on the back of the die, is 3.4°C/W for
the QFN package, and 10°C/W for the TSSOP package.
The LT3030’s internal thermal shutdown circuitry
protects both channels of the device if either channel
experiences an overload or fault condition. Activation
of the thermal shutdown circuitry turns both channels
off. If the overload or fault condition is removed, both
outputs are allowed to turn back on. For continu-
ous normal conditions, do not exceed the maximum
junction temperature rating of 125°C (LT3030E/LT3030I)
or 150°C (LT3030H/LT3030MP).
Carefully consider all sources of thermal resistance from
junction-to-ambient, including additional heat sources
mounted in proximity to the LT3030. For surface mount
devices, use the heat spreading capabilities of the PC board
and its copper traces to accomplish heat sinking. Copper
board stiffeners and plated through-holes can also spread
the heat generated by power devices.
The following tables list thermal resistance as a function of
copper area in a fixed board size. All measurements were
taken in still air on a four-layer FR-4 board with 1oz solid
internal planes, and 2oz external trace planes with a total
board thickness of 1.6mm. For further information on ther-
mal resistance and using thermal information, refer to JEDEC
standard JESD51, notably JESD 51-7 and JESD 51-12.
Calculating Junction Temperature
Example: Channel 1’s output voltage is set to 1.8V.
Channel 2’s output voltage is set to 1.5V. Each channel’s
input voltage is 2.5V. Channel 1’s output current range
is 0mA to 750mA. Channel 2’s output current range is
0mA to 250mA. The application has a maximum ambient
temperature of 50°C. What is the LT3030’s maximum
junction temperature?
The power dissipated by each channel equals:
IOUT(MAX)(VIN – VOUT) + IGND(VIN)
where for output 1:
IOUT(MAX) = 750mA
VIN = 2.5V
IGND at (IOUT = 750mA, VIN = 2.5V) = 13mA
For output 2:
IOUT(MAX) = 250mA
VIN = 2.5V
IGND at (IOUT = 250mA, VIN = 2.5V) = 4.5mA
So, for output 1:
P = 750mA (2.5V – 1.8V) + 13mA (2.5V) = 0.56W
Table 2. UFD Package, 28-Lead QFN
COPPER AREA
TOPSIDE*
2500mm2
1000mm2
225mm2
100mm2
BACKSIDE
2500mm2
2500mm2
2500mm2
2500mm2
BOARD AREA
2500mm2
2500mm2
2500mm2
2500mm2
*Device is mounted on topside.
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
30°C/W
32°C/W
33°C/W
35°C/W
For output 2:
P = 250mA (2.5V – 1.5V) + 4.5mA (2.5V) = 0.26W
The thermal resistance is in the range of 25°C/W to 35°C/W,
depending on the copper area. So, the junction temperature
rise above ambient temperature approximately equals:
(0.56W + 0.26W) 30°C/W = 24.6°C
3030fa
For more information www.linear.com/LT3030
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