LT3060EDC データシートの表示（PDF） - Linear Technology
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LT3060EDC Datasheet PDF : 26 Pages
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LT3060 Series
Applications Information
arrangement allows metal to extend beyond the ends of
the package on the topside (component side) of a PCB.
Connect this metal to GND on the PCB. The multiple IN
and OUT pins of the LT3060 also assist in spreading heat
to the PCB.
For surface mount devices, heat sinking is accomplished
by using the heat spreading capabilities of the PC board
and its copper traces. Copper board stiffeners and plated
through-holes also can spread the heat generated by
power devices.
Tables 2 and 3 list thermal resistance for several different
board sizes and copper areas. All measurements were taken
in still air on a 4 layer FR-4 board with 1oz solid internal
planes and 2oz top/bottom external trace planes with a total
board thickness of 1.6mm. The four layers were electrically
isolated with no thermal vias present. PCB layers, copper
weight, board layout and thermal vias will affect the resul-
tant thermal resistance. For more information on thermal
resistance and high thermal conductivity test boards,
refer to JEDEC standard JESD51, notably JESD51-12 and
JESD51-7. Achieving low thermal resistance necessitates
attention to detail and careful PCB layout.
Table 2. DC Package, 8-Lead DFN
COPPER AREA
TOPSIDE* BACKSIDE BOARD AREA
(mm2)
(mm2)
(mm2)
2500
2500
2500
1000
2500
2500
225
2500
2500
100
2500
2500
50
2500
2500
*Device is mounted on topside
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
48°C/W
49°C/W
50°C/W
54°C/W
60°C/W
Table 3. TS8 Package, 8 Lead TSOT-23
COPPER AREA
TOPSIDE* BACKSIDE BOARD AREA THERMAL RESISTANCE
(mm2)
(mm2)
(mm2)
(JUNCTION-TO-AMBIENT)
2500
2500
2500
57°C/W
1000
2500
2500
58°C/W
225
2500
2500
59°C/W
100
2500
2500
63°C/W
50
2500
2500
67°C/W
*Device is mounted on topside
20
Calculating Junction Temperature
Example: Given an output voltage of 2.5V, an input volt-
age range of 12V ±5%, an output current range of 0mA
to 50mA and a maximum ambient temperature of 85°C,
what will the maximum junction temperature be?
The power dissipated by the device equals:
IOUT(MAX) • (VIN(MAX)–VOUT) + IGND • VIN(MAX)
where,
IOUT(MAX) = 50mA
VIN(MAX) = 12.6V
IGND at (IOUT = 50mA, VIN = 12.6V) = 0.6mA
So,
P = 50mA • (12.6V – 2.5V) + 0.6mA • 12.6V = 0.513W
Using a DFN package, the thermal resistance ranges from
48°C/W to 60°C/W depending on the copper area with
no thermal vias. So the junction temperature rise above
ambient approximately equals:
0.513W • 54°C/W = 27.8°C
The maximum junction temperature equals the maximum
ambient temperature plus the maximum junction tem-
perature rise above ambient or:
TJMAX = 85°C + 27.8°C = 112.8°C
Protection Features
The LT3060 regulators incorporate several protection
features that make it ideal for use in battery-powered
circuits. In addition to the normal protection features
associated with monolithic regulators, such as current
limiting and thermal limiting, the device also protects
against reverse-input voltages, reverse-output voltages
and reverse output-to-input voltages.
Current limit protection and thermal overload protection
protect the device against current overload conditions at
the output of the device. The typical thermal shutdown
temperature is 165°C. For normal operation, do not ex-
ceed a junction temperature of 125°C (LT3060E, LT3060I,
LT3060MP) or 150°C (LT3060H).
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