LT1943
4
1943fa
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. RUN-SS, SS-234 = 2.5V unless otherwise noted.
ELECTRICAL CHARACTERISTICS
PARAMETER CONDITIONS MIN TYP MAX UNITS
SWITCH 4 (350mA INVERTER)
FB4 Voltage 1.23 1.25 1.27 V
● 1.22 1.27 V
FB4 Voltage Line Regulation 4.5V < V
IN
< 22V 0.01 0.03 %/V
FB4 Pin Bias Current (Note 4) ● 100 600 nA
NFB4 Voltage (V
FB4
-V
NFB4
) 1.215 1.245 1.275 V
● 1.205 1.275 V
NFB4 Voltage Line Regulation 4.5V < V
IN
< 22V 0.01 0.03 %/V
NFB4 Pin Bias Current (Note 5) 100 600 nA
Error Amplifier 4 Voltage Gain 200 V/V
Error Amplifier 4 Transconductance ∆I = 5µA 450 µmhos
Switch 4 Current Limit ● 0.35 0.5 0.7 A
Switch 4 V
CESAT
I
SW4
= 0.3A 260 390 mV
Switch 4 Leakage Current FB4 = 1.5V 0.1 1 µA
BIAS Pin Current due to SW4 I
SW4
= 0.3A 15 mA
Maximum Duty Cycle (SW4) 84 88 %
● 83 %
TYPICAL PERFOR A CE CHARACTERISTICS
UW
DUTY CYCLE (%)
0
SW1 CURRENT (A)
5
4
3
2
1
0
20 40 60 80
1943 G02
100
TEMPERATURE (°C)
–50
SW1 CURRENT (A)
4.5
4.0
3.5
3.0
2.5
0
50
75
1943 G03
–25
25
100
125
INPUT VOLTAGE (V)
0
V
LOGIC
MAXIMUM OUTPUT CURRENT (A)
2.0
2.2
2.4
20
1943 G01
1.8
1.6
1.2
5
10
15
1.4
2.8
2.6
L1 = 4.7µH
L1 = 3.3µH
TYPICAL
MINIMUM
T
A
= 25°C T
A
= 25°C
Maximum Output Current
for V
LOGIC
= 3.3V
SW1 Current Limit vs Duty Cycle SW1 Current Limit
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1943E 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 3: The C
T
pin is held low until FB1, FB2, FB3 and FB4 all ramp above
the FB threshold offset.
Note 4: Current flows into FB1, FB2, FB3 and FB4 pins.
Note 5: Current flows out of NFB4 pin.
Note 6: Current limit is guaranteed by design and/or correlation to static
test. Slope compensation reduces current limit at high duty cycle.
Note 7: This is the minimum voltage across the boost capacitor needed to
guarantee full saturation of the internal power switch.
