Datasheet

LTC3443
10
3443fa
A detailed diagram of this function is shown in Figure 5.
The components R
SS
and C
SS
provide a slow ramping
voltage on the SHDN/SS pin to provide a soft-start
function.
SOFT-START
The soft-start function is combined with shutdown. When
the SHDN/SS pin is brought above typically 1V, the IC is
enabled but the EA duty cycle is clamped from the V
C
pin.
OPERATIO
U
9
PV
IN
A
4
SW1
6
GND
5
SW2
L
+–
8
V
OUT
D
C
800mA
I
INDUCTOR
0mA
3443 F03
T1
B
dI
dt
V
IN
L
≈
9
PV
IN
A
4
SW1
6
GND
5
SW2
L
–+
8
V
OUT
D
C
800mA
I
INDUCTOR
0mA
3443 F04
T2
B
dI
dt
V
OUT
L
≈ –
–
+
12
11
V
IN
ERROR AMP
1.22V
14μA
FB
R1
R2
C
P1
V
C
V
OUT
1
SHDN/SS
C
SS
1V
ENABLE SIGNAL
R
SS
SOFT-START
CLAMP
TO PWM
COMPARATORS
CHIP
ENABLE
3443 F05
–
+
V
CI
Figure 3. Inductor Charge Cycle During Burst Mode Operation Figure 4. Inductor Discharge Cycle During Burst Mode Operation
Figure 5. Soft-Start Circuitry