LT3024IDE datasheet(16/20 Pages) LINER

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LT3024

3024fa

APPLICATIONS INFORMATION

and its copper traces. Copper board stiffeners and plated

through-holes can also be used to spread the heat gener-

ated by power devices.

The following tables list thermal resistance for several

different board sizes and copper areas. All measurements

were taken in still air on 3/32" FR-4 board with one ounce

copper.

Table 1. FE Package, 16-Lead TSSOP

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

38°C/W

1000mm2

2500mm2

43°C/W

225mm2

2500mm2

48°C/W

100mm2

2500mm2

60°C/W

*Device is mounted on topside.

Table 2. UE Package, 12-Lead DFN

COPPER AREA

BOARD AREA

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

TOPSIDE*

BACKSIDE

2500mm2

40°C/W

1000mm2

2500mm2

45°C/W

225mm2

2500mm2

50°C/W

100mm2

2500mm2

62°C/W

*Device is mounted on topside.

The thermal resistance junction-to-case (

θJC), measured

at the Exposed Pad on the back of the die is 10°C/W for

the DFN package and 8°C/W for the TSSOP package.

Calculating Junction Temperature

Example: Given Output 1 set for an output voltage of

3.3V, Output 2 set for an output voltage of 2.5V, an input

voltage range of 3.8V to 5V, an output current range of

0mA to 500mA for Output 1, an output current range of

0mA to 100mA for Output 2 and a maximum ambient

temperature of 50°C, what will the maximum junction

temperature be?

The power dissipated by each output will be equal to:

IOUT(MAX)(VIN(MAX) – VOUT) + IGND(VIN(MAX))

Where for Output 1:

IOUT(MAX) = 500mA

VIN(MAX) = 5V

IGND at (IOUT = 500mA, VIN = 5V) = 9mA

For Output 2:

IOUT(MAX) = 100mA

VIN(MAX) = 5V

IGND at (IOUT = 100mA, VIN = 5V) = 2mA

So for Output 1:

P = 500mA (5V – 3.3V) + 9mA (5V) = 0.90W

For Output 2:

P = 100mA (5V – 2.5V) + 2mA (5V) = 0.26W

The thermal resistance will be in the range of 35°C/W to

55°C/W depending on the copper area. So the junction

temperature rise above ambient will be approximately

equal to:

(0.90W + 0.26W) 50°C/W = 57.8°C

The maximum junction temperature will then be equal to

the maximum junction temperature rise above ambient

plus the maximum ambient temperature or:

TJMAX = 50°C + 57.8°C = 107.8°C

Protection Features

The LT3024 regulator incorporates several protection fea-

tures which 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 is protected against reverse

input voltages, reverse output voltages and reverse voltages

from output to input. The two regulators have common

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