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SETTING THE SOFT-START TIMES
To prevent rush currents when the IC is turned on, you can set a soft-start by connecting soft-start capacitors
(C
) to the CSCP terminal (pin 2). When IC starts (V
SCP
capacitors (C
) connected to CSCP terminal are charged at 11 A. The error amplifier output (FB (pin 8) ) is
SCP
determined by comparison between the lower one of the potentials at two non-inverted input terminals (0.5 V
in an internal reference voltage, CSCP terminal voltages) and the inverted input terminal voltage ( INE (pin 1)
voltage).
The FB terminal voltage is decided for the soft-start period by the comparison between 0.5 V in an internal
reference voltage and the voltages of the CSCP terminal. The DC/DC converter output voltage rises in proportion
to the CSCP terminal voltage as the soft-start capacitor connected to the CSCP terminal is charged.
The soft-start time is obtained from the following formula:
Soft-start time: ts (time to output 100%)
ts (s) : = 0.045
C
( F)
SCP
: = 0.8 V
: = 0.5 V
: = 0 V
• Soft-Start Circuit
V
O
R1
R2
Error Amp block INE voltage
Soft-start time (ts)
VREF
INE
1
2
CSCP
C
SCP
8
FB
UVLO threshold voltage), the external soft-start
CC
CSCP terminal voltage
11 A
L priority
(0.5 V)
MB39A105
t
Error Amp
UVLO
13
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