LT3029IDE datasheet(15/20 Pages) LINER

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LT3029

3029f

APPLICATIONS INFORMATION

Thermal Considerations

The LT3029’s power handling capability limits the maximum

rated junction temperature (125°C, LT3029E/LT3029I/

LT3029MP or 150°C, LT3029H). Two components comprise

the power dissipated by each channel:

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.

Power dissipation for each channel equals the sum of the

two components listed above. Total power dissipation for

the LT3029 equals the sum of the power dissipated by

each channel.

The LT3029’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 continuous normal conditions, do

not exceed the maximum junction temperature rating of

125°C(LT3029E/LT3029I/LT3029MP)or150°C(LT3029H).

Carefully consider all sources of thermal resistance from

junction-to-ambient, including additional heat sources

mounted in proximity to the LT3029. 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 thermal resistance and using thermal information, refer

to JEDEC standard JESD51, notably JESD51-12.

Table 2. DE Package, 16-Lead DFN

COPPER AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

BOARD AREA

2500mm2

36°C/W

1000mm2

2500mm2

37°C/W

225mm2

2500mm2

38°C/W

100mm2

2500mm2

40°C/W

*Device is mounted on topside.

Table 3. MSE Package, 16-Lead MSOP

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

35°C/W

1000mm2

2500mm2

36°C/W

225mm2

2500mm2

37°C/W

100mm2

2500mm2

39°C/W

*Device is mounted on topside.

The junction-to-case thermal resistance (

θJC), measured

at the Exposed Pad on the back of the die, is 4.3°C/W for

the DFN package, and 5°C/W to 10°C/W for the MSOP

package.

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