LTC3442 Datasheet, PDF (12/20 Pages) Linear Integrated Systems – Micropower Synchronous Buck-Boost DC/DC Converter with Automatic Burst Mode Operation

LTC3442
U
OPERATIO
response, Type 3 compensation is also recommended to
broad band the control loop and roll off past the two pole
response of the output LC filter. (See Closing the Feedback
Loop.)
Soft-Start
The soft-start function is combined with shutdown. When
the SHDN/SS pin is brought above 1V typical, the IC is
enabled but the EA duty cycle is clamped from V_C. A
detailed diagram of this function is shown in Figure 5. The
components R_SS and C_SS provide a slow ramping voltage
on SHDN/SS to provide a soft-start function. To ensure
that V_C is not being clamped, SHDN/SS must be raised
above 2.4V.
V_IN
14µA
SOFT-START
CLAMP
TO PWM
V_CI
COMPARATORS
CHIP
ENABLE
ERROR AMP
1.22V
FB
12
V_C ^CP1
11
V_OUT
R1
R2
SHDN/SS
1
R_SS
C_SS
ENABLE SIGNAL
3442 F05
1V
Figure 5. Soft-Start Circuitry
3442f
12