BD9540EFV Datasheet, PDF (8/18 Pages) Rohm – 2ch Switching Regulators for Desktop PC

BD9540EFV
Technical Note
●Explanation of Operation
The BD9540EFV is a 2ch switching regulator controller incorporating ROHM’s proprietary H³Reg^TM CONTROLLA control
system. When VOUT drops due to a rapid load change, the system quickly restores VOUT by extending the TON time
interval.
H³Reg^TM control
(Normal operation)
FB
REF
When FB falls below the threshold voltage (REF), a drop
is detected, activating the H³Reg^TM CONTROLLA system.
HG
tON= ^VOUT × ¹ [sec]・・・(1)
VIN
f
LG
HG output is determined by the formula above. (See P13)
LG output operates until FB voltage falls below REF
voltage after HG becomes OFF.
(VOUT drops due to a rapid load change)
FB
REF
Io
HG
LG
When FB (VOUT) drops due to a rapid load change, and the
voltage remains below REF after the programmed tON time
interval has elapsed, the system quickly restores VOUT by
extending the tON time, improving transient response.
●Timing Chart
・Soft Start Function
EN
1msec
VOUT
IIN
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.
Rush current:
IIN = ^Co×VOUT
1ms
[A] ・・・(2)
(Co: All capacitors connected with VOUT)
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8/17
2009.04 - Rev.B