Datasheet

3
LT1949
TYPICAL PERFOR A CE CHARACTERISTICS
UW
INPUT VOLTAGE
0
OSCILLATOR FREQUENCY (kHz)
700
650
600
550
500
2468
1949 G01
10 12
25°C
–40°C
85°C
Oscillator Frequency
Switch Current Limit,
Duty Cycle = 30%
Switch Current Limit
TEMPERATURE (°C)
–50
SWITCH CURRENT (A)
1.3
1.2
1.1
1.0
0.9
0.8
–25
02550
1949 G03
75 100
Switch Voltage Drop (V
CESAT
)
Feedback Voltage
TEMPERATURE (°C)
–50
FEEDBACK VOLTAGE (V)
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
QUIESCENT CURRENT (mA)
1949 G06
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
0 255075100
SWITCH CURRENT (A)
0
SWITCH VOLTAGE (V)
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.
The ● denotes specifications which apply over the full operating
temperature range, otherwise specifications are T
A
= 25°C. V
IN
= 2V, V
SHDN
= 2V unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Switch V
CESAT
I
SW
= 800mA 410 mV
I
SW
= 500mA ● 400 mV
Reference Line Regulation 1.8V ≤ V
IN
≤ 12V ● 0.08 0.15 %/V
SHDN Input Voltage High ● 1.4 6 V
SHDN Input Voltage Low ● 0.4 V
ELECTRICAL CHARACTERISTICS
DUTY CYCLE (%)
0
SWITCH CURRENT (A)
1.3
1.2
1.1
1.0
0.9
0.8
80
1949 G02
20
40
60
100