3

LT1949

TYPICAL PERFOR A CE CHARACTERISTICS

INPUT VOLTAGE

0

700

650

600

550

500

24

6

8

1949 G01

10

12

25

°C

–40

°C

85

°C

Oscillator Frequency

Switch Current Limit,

Duty Cycle = 30%

Switch Current Limit

TEMPERATURE (

°C)

–50

1.3

1.2

1.1

1.0

0.9

0.8

–25

025

50

1949 G03

75

100

Feedback Voltage

TEMPERATURE (

°C)

–50

1.25

1.24

1.23

1.22

1.21

1.20

–25

0

25

50

1949 G05

75

100

Quiescent Current, SHDN = 2V

TEMPERATURE (

°C)

–50

–25

1949 G06

4.6

4.5

4.4

4.3

4.2

4.1

4.0

3.9

3.8

0

255075

100

SWITCH CURRENT (A)

0

1.0

0.8

0.6

0.4

0.2

0

0.2

0.4

0.6

0.8

1949 G04

1.0

1.2

85

°C

–40

°C

25

°C

Note 3: Bias current flows into FB pin.

Note 4: Switch current limit guaranteed by design and/or correlation to

static tests. Duty cycle affects current limit due to ramp generator.

Note 5: Bias current flows out of LBI pin.

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: The LT1949E is guaranteed to meet performance specifications

from 0

°C to 70°C. Specifications over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process controls.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

410

mV

q

400

mV

Reference Line Regulation

1.8V

q

0.08

0.15

%/V

SHDN Input Voltage High

q

1.4

6

V

SHDN Input Voltage Low

q

0.4

V

ELECTRICAL CHARACTERISTICS

DUTY CYCLE (%)

0

1.3

1.2

1.1

1.0

0.9

0.8

80

1949 G02

20

40

60

100