05S_1XC9201/9202新規 02.09.12 15:16 ページ 546
XC9201Series
ꢀ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 according to values of Vcont, RSS, and
CSS.
T=-Css x Rss x ln((Vcont-1.55)/Vcont)
Example: When Css=0.1µF,Rss=470kΩ, and Vcont=5V, T=-0.1e-6 × 470e3 × In((5-1.55)/5)=17.44ms.
CE/SS pin
Rss
〔Inside the IC〕�
CE,�
To Verr amplifier
Vref circuit
UVLO
Vcont
Css
Set the soft start time to a value sufficiently longer than the period of a clock pulse.
> Circuit example 1: N-ch open drain
5
Vcont
〔Inside the IC〕�
Rss
CE/SS pin
ON/OFF signal
Css
> Circuit example 2: CMOS logic (low current dissipation)
Vcont
〔Inside the IC〕�
Rss
ON/OFF signal
CE/SS pin
Css
> Circuit example 3: CMOS logic (low current dissipation), quick off
Vcont
〔Inside the IC〕�
CE/SS pin
Rss
ON/OFF signal
Css
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TOREX [ Torex Semiconductor ]
