Technical Note

8/14

BD8628EFV, BD8624EFV

www.rohm.com

2009.05 - Rev.A

© 2009 ROHM Co., Ltd. All rights reserved.

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Operation description

ON/OFF control

DC/DC converter ON/OFF function

DC/DC converter controller can be controlled ON/OFF by CTL terminal.

Analog circuit starts operation at ON control (on mode), and goes down to setting output voltage.

Analog circuit should be standby at OFF control (off mode), and output voltage becomes 0V.

Table2 DC/DC converter ON/OFF function

CTL terminal voltage

>VIHCTL

ON control

<VILCTL

OFF control

Soft start time set function

DC/DC converter can do soft start without overshoot by charging soft start capacity (Css) connected between SS terminal

and GND by charging current at ON control.

Also, soft start time (tss) can be set by setting soft start capacity arbitrarily.

Soft start time (tss) should be set at 3msec < tss < 30msec.

※

Please note that the overshoot is not caused in the output setting voltage when setting it to tss≦3msec.

SS

SS

SSTH

SS

I

C

V

t





Discharge function

DC/DC converter can do soft off by discharging load discharged to soft start capacity connected between SS terminal to

GND by discharging resistance at OFF control.

Soft off operates in proportion to the voltage of the terminal SS the output voltage from the point of VSS=0.8V (typ).

Figure.3 Wave form at ON/OFF control