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LT1945 Datasheet PDF : 8 Pages
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LT1945
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 1.2V, VSHDN = 1.2V unless otherwise noted.
PARAMETER
SHDN Pin Current
SHDN Input Voltage High
SHDN Input Voltage Low
Switch Leakage Current
CONDITIONS
VSHDN = 1.2V
VSHDN = 5V
Switch Off, VSW = 5V
MIN TYP MAX UNITS
2
3
μA
8
12
μA
0.9
V
0.25
V
0.01
5
μA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may
cause permanent damage to the device. Exposure to any Absolute Maximum
Rating condition for extended periods may affect device reliability and lifetime.
Note 2: The LT1945E is guaranteed to meet performance specifications
from 0°C to 70°C junction temperature. Specifications over the –40°C
to 85°C operating junction temperature range are assured by design,
characterization and correlation with statistical process controls. The
LT1945I is guaranteed over the full –40°C to 125°C operating junction
temperature range.
Note 3: Bias current flows out of the NFB1 pin.
Note 4: Bias current flows into the FB2 pin.
Note 5: See Figure 1 for Switcher 1 and Switcher 2 locations.
TYPICAL PERFORMANCE CHARACTERISTICS
Switch Saturation Voltage
(VCESAT)
0.60
0.55
0.50
0.45
ISWITCH = 500mA
0.40
0.35
0.30
ISWITCH = 300mA
0.25
0.20
0.15
0.10
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
1945 G01
FB2 Pin Voltage and
Bias Current
1.25
1.24
VOLTAGE
1.23
1.22
CURRENT
1.21
1.20
–50
–25 0 25 50
TEMPERATURE (°C)
50
40
30
20
10
0
75 100
1945 G02
NFB1 Pin Voltage and
Bias Current
–1.25
5
–1.24
4
VOLTAGE
–1.23
3
–1.22
–1.21
2
CURRENT
1
–1.20
–50 –25 0
0
25 50 75 100
TEMPERATURE (°C)
1945 G03
Switch Off Time
550
500
450
400
VIN = 1.2V
VIN = 12V
350
300
250
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
1945 G04
Switch Current Limit
400
VIN = 12V
350
300
VIN = 1.2V
250
200
150
100
50
0
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
1945 G05
Quiescent Current
25
VFB = 1.23V
NOT SWITCHING
23
21
VIN = 12V
19
VIN = 1.2V
17
15
–50 –25 0
25 50 75 100
TEMPERATURE (°C)
1945 G06
1945fa
3
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