Technical Note

10/18

BD9536FV

www.rohm.com

2010.07 - Rev.A

© 2010 ROHM Co., Ltd. All rights reserved.

●

Explanation of Operation

The BD9536FV is a 2ch switching regulator controller incorporating ROHM’s proprietary H

When VOUT drops due to a rapid load change, the system quickly restores VOUT by extending the TON time interval.

H

(Normal operation)

(VOUT drops due to a rapid load change)

●

Timing Chart

・

Soft Start Function

Rush current:

IIN = Co

×

VOUT

Tss

[A]

・・・

(2)

・・・

(3)

When FB falls below the threshold voltage (REF), a drop

is detected, activating the H

HG output is determined by the formula above.

the voltage remains below REF after the programmed

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 timing

and input current are determined via formula (2) and (3)

below.

Soft start time:

(Css: Soft start capacitor; Co: Output capacitor)

FB

REF

HG

LG

EN

REF

IIN

FB

REF

HG

Io

LG

REF

VIN

×

1

f

[sec]・・・(1)