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TSZ02201-0J3J0AJ00120-1-2

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ROHM Co., Ltd. All rights reserved.

10/20

02.MAR.2012 Rev.001

TSZ22111･15･001

BD9123MUV

Datasheet

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.

The inclination of standing up is different and the soft start time is different because of constancy depending on the value

offset output voltage.

When 1V settiing it, it is Tss=1msec(Typ.)

Fig.25 Soft start action

・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 0µA(Typ.).

・UVLO function

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

And the hysteresis width

of 50mV (Typ.) is provided to prevent output chattering.

Fig.26 Soft start, Shutdown, UVLO timing chart

・PGOOD function

When the output voltage falls below 75% (Typ.) of a set value, the PGOOD pin of Open-Drain is turned off. And the

hysteresis width of 15% (Typ.) is provided to prevent output chattering.

Fig.27 PGOOD timing chart

UVLO

EN

UVLO

UVLO

Hysteresis 50mV

Tss

Tss

Tss

Soft start

Standby mode

Operating mode

Standby

mode

Operating mode

Standby

mode

Operating mode

Standby mode

EN

Vcc

VOUT

VCC,EN

Tss

Tss’

1.2V

0.85V

[ms]

VOUT

90%

The hysteresis width

VOUT

75%

PGOOD