Datasheet

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