BD9102FVM, BD9104FVM, BD9106FVM

Technical Note

10/17

www.rohm.com

2009.05 - Rev.A

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

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Description of operations

・

Soft-start function

EN terminal shifted to “High” activates a soft-starter to gradually establish the output voltage with the current limited during

startup, by which it is possible to prevent an overshoot of output voltage and an inrush current.

・

Shutdown function

With EN terminal shifted to “Low”, the device turns to Standby Mode, and all the function blocks including reference

voltage circuit, internal oscillator and drivers are turned to OFF. Circuit current during standby is 0 μF (Typ.).

・

UVLO function

Detects whether the input voltage sufficient to secure the output voltage of this IC is supplied. And the hysteresis width of

100 mV (Typ.) is provided to prevent output chattering.

・

BD9102FVM BD9104FVM

・

BD9106FVM

Fig.47 Soft start, Shutdown, UVLO timing chart

・

Short-current protection circuit with time delay function

Turns OFF the output to protect the IC from breakdown when the incorporated current limiter is activated continuously for

at least 1 ms. The output thus held tuned OFF may be recovered by restarting EN or by re-unlocking UVLO.

Fig.48 Short-current protection circuit with time delay timing chart

Hysteresis 100mV

Tss

Tss

Tss

Soft start

Standby mode

Operating mode

Standby

mode

Operating mode

Standby

mode

Operating mode

Standby mode

UVLO

EN

UVLO

UVLO

EN

1msec

Output OFF

latch

EN

Limit

Standby

mode

Operating mode

Standby

mode

Operating mode

EN

Timer latch

EN