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OPERATIONAL EXPLANATION (Continued)

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Functional Settings

1. Soft Start

CE and soft start (SS) functions are commonly assigned to the CE/SS pin. The soft start function is effective until the

voltage at the CE pin reaches approximately 1.55 V rising from 0 V. Soft start time is approximated by the equation below

T = -0.1 x 10

CE/SS pin

Vcont

Css

CE,

UVLO

Vref

circuit

To Verr amplifier

Rss

Set the soft start time to a value sufficiently longer than the period of a clock pulse.

> Circuit example 1: N-ch open drain

CE/SS pin

Css

Rss

ON/OFF signal

Vcont

> Circuit example 2: CMOS logic (low supply current)

CE/SS pin

Css

Rss

ON/OFF signal

Vcont

> Circuit example 3: CMOS logic (low supply current), quick off

CE/SS pin

Css

Rss

ON/OFF signal

Vcont