Datasheet

BD9540EFV
Technical Note
8/17
www.rohm.com
2009.04 - Rev.B
© 2009 ROHM Co., Ltd. All rights reserved.
●Explanation of Operation
The BD9540EFV is a 2ch switching regulator controller incorporating ROHM’s proprietary H
3
Reg
TM
CONTROLLA control
system. When VOUT drops due to a rapid load change, the system quickly restores VOUT by extending the TON time
interval.
H
3
Reg
TM
control
(Normal operation)
(VOUT drops due to a rapid load change)
●Timing Chart
・Soft Start Function
Rush current:
IIN =
Co×V
OUT
1ms
[A]
t
ON=
V
OUT
VIN
×
1
f
[sec]・・・(1)
・・・(2)
When FB falls below the threshold voltage (REF), a drop
is detected, activating the H
3
Reg
TM
CONTROLLA system.
HG output is determined by the formula above. (See P13)
LG output operates until FB voltage falls below REF
voltage after HG becomes OFF.
When FB (V
OUT) drops due to a rapid load change, and the
voltage remains below REF after the programmed t
ON time
interval has elapsed, the system quickly restores VOUT by
extending the t
ON time, improving transient response.
Soft start is utilized when the EN pin is set high. Current
control takes effect at startup, enabling a moderate
“ramping start” on the output voltage. Soft start time is
1msec. And input current is determined via formula
(2) below.
(Co: All capacitors connected with VOUT)
FB
REF
HG
LG
EN
IIN
1msec
V
OUT
FB
REF
HG
Io
LG