LT3015 データシートの表示（PDF） - Linear Technology

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LT3015

1.5A, Low Noise, Negative Linear Regulator with Precision Current Limit

Linear Technology 

LT3015 Series

APPLICATIONS INFORMATION

Table 2. Measured Thermal Resistance for DFN Package

COPPER AREA

TOP SIDE* BACKSIDE

BOARD THERMAL RESISTANCE

AREA (JUNCTION-TO-AMBIENT)

2500mm2 2500mm2 2500mm2

40°C/W

1000mm2

225mm2

2500mm2

2500mm2

2500mm2

2500mm2

40°C/W

41°C/W

100mm2 2500mm2 2500mm2

42°C/W

*Device is mounted on topside

Table 3. Measured Thermal Resistance for MSOP Package

COPPER AREA

TOP SIDE*

2500mm2

BACKSIDE

2500mm2

BOARD

AREA

2500mm2

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

37°C/W

1000mm2 2500mm2 2500mm2

37°C/W

225mm2 2500mm2 2500mm2

38°C/W

100mm2 2500mm2 2500mm2

40°C/W

*Device is mounted on topside

Table 4. Measured Thermal Resistance for DD-Pak Package

COPPER AREA

TOP SIDE*

2500mm2

1000mm2

225mm2

BACKSIDE

2500mm2

2500mm2

2500mm2

BOARD

AREA

2500mm2

2500mm2

2500mm2

THERMAL RESISTANCE

(JUNCTION-TO-AMBIENT)

14°C/W

16°C/W

19°C/W

*Device is mounted on topside

T Package, 5-Lead TO-220

Thermal Resistance (Junction-to-Case) = 3°C/W

Calculating Junction Temperature

Example: Given an output voltage of –2.5V, an input voltage

range of –3.3V ± 5%, an output current range of 1mA to

500mA, and a maximum ambient temperature of 85°C,

what is the maximum junction temperature?

The power dissipated by the LT3015 equals:

IOUT(MAX) • (VIN(MAX) - VOUT) + IGND • (VIN(MAX))

where:

IOUT(MAX) = –500mA

VIN(MAX) = –3.465V

IGND at (IOUT = –500mA, VIN = –3.465V) = –6.5mA

Thus:

P = –500mA(–3.465V + 2.5V) + –6.5mA • (–3.465V) =

0.505W

Using a DFN package, the thermal resistance is in the

range of 40°C/W to 42°C/W depending on the copper area.

Therefore, the junction temperature rise above ambient

approximately equals:

0.505W • 41°C/W = 20.7°C

The maximum junction temperature equals the maxi-

mum ambient temperature plus the maximum junction

temperature rise above ambient or:

TJMAX = 85°C + 20.7°C = 105.7°C

Protection Features

The LT3015 incorporates several protection features that

make it ideal for use in battery-powered applications. In

addition to the normal protection features associated

with monolithic regulators, such as current limiting and

thermal limiting, the device protects itself against reverse

input voltages and reverse output voltages.

Precision current limit and thermal overload protections

are intended to protect the LT3015 against current over-

load conditions at the output of the device. For normal

operation, do not allow the the junction temperature to

exceed 125°C.

Pulling the LT3015’s output above ground induces no

damage to the part. If IN is left open circuit or grounded,

OUT can be pulled above GND by 30V. In addition, OUT acts

like an open circuit, i.e. no current flows into the pin. If IN

is powered by a voltage source, OUT sinks the LT3105’s

short-circuit current and protects itself by thermal limiting.

In this case, grounding the SHDN pin turns off the device

and stops OUT from sinking the short-circuit current.

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