Datasheet

LT1940/LT1940L
4
1940fa
Current Limit vs Duty Cycle
V
OUT
vs Temperature
Frequency Foldback
I
RUN/SS
vs Temperature
TYPICAL PERFOR A CE CHARACTERISTICS
UW
DUTY CYCLE (%)
0
CURRENT LIMIT (A)
TYPICAL
80
1940 G08
20
40
60
100
3.0
2.5
2.0
1.5
1.0
0.5
0
MINIMUM
–50
–25
0 25 50 75 100 125
TEMPERATURE (°C)
V
OUT
(V)
1940 G09
3.40
3.35
3.30
3.25
3.20
CHANNEL 1, FIGURE 1, V
IN
= 12V
SWITCH CURRENT (A)
0
BOOST CURRENT (mA)
20
30
2.0
1940 G07
10
0
0.5
1.0
1.5
40
Frequency vs Temperature
Boost Pin Current
TEMPERATURE (°C)
–50
FREQUENCY (MHz)
1.3
1.2
1.1
1.0
0.9
–25 0 25 50
1940 G10
75 100 125
FEEDBACK VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1940 G11
0
0.2
0.4 0.6 0.8 1.0 1.2
TEMPERATURE (°C)
–50
0
RUN/SS CURRENT (µA)
0.5
1.0
1.5
2.0
3.0
–25
02550
1940 G12
75 100 125
2.5
Maximum Load Current,
V
OUT
= 1.8V
Switch V
CESAT
Maximum Load Current,
V
OUT
= 3.3V
SW CURRENT (A)
0
SWITCH VOLTAGE (mV)
200
300
2.0
1940 G06
100
0
0.5
1.0
1.5
400
T
A
= 25°C
INPUT VOLTAGE (V)*
0
LOAD CURRENT (A)
1.4
1.6
12 14
1940 G04
1.2
1.0
842
6
10
16
1.8
L = 2.2µH
L = 1.5µH
L = 1µH
INPUT VOLTAGE (V)*
0
LOAD CURRENT (A)
1.4
1.6
20
1940 G05
1.2
1.0
5
10
15
25
1.8
L = 4.7µH
L = 3.3µH
L = 2.2µH
SLOPE COMPENSATION REQUIRES
L > 2.2µH FOR V
IN
< 7 WITH V
OUT
= 3.3V
*Maximum V
IN
is 7V for LT1940L.