5

LT1506

Frequency Foldback

FEEDBACK PIN VOLTAGE (V)

0

500

400

300

200

100

0

2.0

1506 G10

0.5

1.0

1.5

2.5

SWITCHING

FREQUENCY

FEEDBACK PIN

CURRENT

Inductor Core Loss for 3.3V Output

INDUCTANCE (

µH)

02

1.0

0.1

0.01

0.001

46

8

10

1506 G01

TYPE 52

Metglas

®

Kool M

PERMALLOY

µ = 125

Switching Frequency

TEMPERATURE (

°C)

–50

550

540

530

520

510

500

490

480

470

460

450

100

1506 G11

–25

0

25

50

75

125

BOOST Pin Current

SWITCH CURRENT (A)

0

0

10

20

40

30

60

50

12

3

45

1506 G14

80

70

100

90

DUTY CYCLE = 100%

Maximum Load Current

INPUT VOLTAGE (V)

4

4.0

4.2

4.4

12

1506 G13

3.8

3.6

610

814

3.4

3.2

3.0

L= 10

µH

L= 5

µH

L= 3

µH

L= 1.8

µH

Maximum Load Current

INPUT VOLTAGE (V)

5

2.6

2.8

3.2

3.4

3.6

9

13

15

4.4

1506 G17

3.0

711

3.8

4.0

4.2

L= 10

µH

L= 5

µH

L= 3

µH

L= 1.8

µH

Switch Voltage Drop

SWITCH CURRENT (A)

0

250

200

400

125

°C

25

°C

350

300

45

1506 G16

150

100

50

0

1

2

3

500

450

–40

°C

JUNCTION TEMPERATURE (

°C)

–50

1.4

1.2

1.0

0.8

0.6

0.4

100

1506 G15

–25

0

25

50

75

125

SHUTDOWN

OUTPUT VOLTAGE (%)

0

5

6

7

80

1506 G18

4

3

20

40

60

100

2

1

0

FOLDBACK

CHARACTERISTICS

CURRENT

SOURCE

LOAD

RESISTOR

LOAD

MOS LOAD

POSSIBLE UNDESIRED

STABLE POINT FOR

CURRENT SOURCE

LOAD*

Current Limit Foldback

Kool M

µ is a registered trademark of Magnetics, Inc.

Metglas is a registered trademark of AlliedSignal Inc.

*See “More Than Just Voltage Feedback” in the Applications Information section.