mb3778pfv Fujitsu Microelectronics, Inc., mb3778pfv Datasheet - Page 16

• Manufacturer Part Number: mb3778pfv
• Description: Switching Regulator Controller
• Manufacturer: Fujitsu Microelectronics, Inc.

16
MB3778
SETTING THE SOFT START TIME
When power is switched on, the current begins charging the capacitor (C
6). The soft start process operates by comparing the soft start setting voltage, which is proportional to the DTC1
terminal voltage, with the triangular waveform, and varying the ON-duty of the OUT terminal (pin 7).
The soft start time until the ON duty reaches 50
Soft start time (time until output ON duty
ts (s) : =
For example, if Ra
ts (s) : = 0.1
• Soft Start on DCT1 terminal (DTC2 is similar)
C
DTC1
C
DTC1
Ra
( F)
4.7 k and Rb
Rb
(Ra
Rb)
10 k , the result is:
ln (1
50 ) .
1.6 (Ra
is determined by the following equation:
DTC1
V
REF
Rb)
16
6
(2.46 Rb) )
Ra
Rb
DTC1
) connected the DTC1 terminal (pin
C
DTC1