LT1940/LT1940L
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 5V, VBOOST = 8V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
= 0V
MIN
TYP
150
2.4
MAX
UNITS
kHz
A
Foldback Frequency
Switch Current Limit
V
FB
Note 3
1.8
3.2
320
10
Switch V
I
= 1A
210
mV
µA
V
CESAT
SW
Switch Leakage Current
Minimum Boost Voltage Above Switch (Note 4)
BOOST Pin Current
I
I
= 1A
= 1A
1.8
20
2.5
30
SW
SW
mA
µA
V
RUN/SS Current
2.3
0.6
125
0.22
0.1
RUN/SS Threshold
0.3
90
PG Threshold Offset
V
V
V
Rising
160
0.4
1
mV
V
FB
FB
PG
PG Voltage Output Low
PG Pin Leakage
= 1V, I = 250µA
PG
= 2V
µA
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 3: Current limit is guaranteed by design and/or correlation to static
test. Slope compensation reduces current limit at high duty cycle.
Note 2: The LT1940E 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.
Note 4: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
Efficiency, VOUT = 3.3V
Efficiency, VOUT = 1.8V
Efficiency, VOUT = 5V
100
90
80
70
60
90
80
70
60
50
100
90
80
70
60
50
V
= 1.8V
V
= 5V
V
= 3.3V
OUT
L = 2.2µH (SUMIDA CR43-2R2)
= 25°C
OUT
L = 4.7µH (SUMIDA CR43-4R7)
= 25°C
OUT
L = 3.3µH (SUMIDA CR43-3R3)
= 25°C
T
A
T
A
T
A
V
= 5V
IN
V
= 8V
IN
V
= 5V
IN
V
= 12V
IN
V
= 12V
IN
V
= 18V
IN
V
= 18V
IN
0
0.5
1.0
1.5
0
0.5
1.0
1.5
0
0.5
1.0
1.5
LOAD CURRENT (A)
LOAD CURRENT (A)
LOAD CURRENT (A)
1940 G03
1940 G01
1940 G02
1940fa
3
Linear [ Linear ]
