MB3827 Datasheet, PDF (24/41 Pages) Fujitsu Component Limited. – 6-ch DC/DC Converter IC With Synchronous Rectification for voltage step-up and step-down

MB3827
(2) Setting Methods
• Channel 7 soft start interval
Before CTL1-4, 7 are ON: Vin is applied along path (A) below and charges CFB7.
After CTL1-4, 7 are ON: Along path (B), CFB7 is discharged by R2, R3, D1 at I1 to 15 µA on a time constant,
and with the fall of V-IN7-1, channel 7 is activated with a soft start.
Note : The short detection function is suspended while VDTC is below 0.6V.
Channel 7 equivalent circuit of soft start section
FB7
CFB7
−IN7−1
VSS (O)
+IN7
R1
100 kΩ
A
B
Error
Amp.7
−
+
R3
10 kΩ
100 kΩ
Vin
−IN7−2
: Before CTL1-4, 7 are ON
: After CTL1-4, 7 are ON
D1
R2
60 kΩ
I1
15 µA
Channel 7 soft start operating waveform
V −IN7−1
(V)
VDTC7
VCT
VFB7
VSS (O)
VFB7
VCT
0.6 V
VDTC7
=: 1.55 V
VSS (O)
V −IN7−1
0.8 V
0.77 V
0.3 V
t
CTL1−4, 7
Soft start operate
Short detection suspended during this interval
24