XC9201
Series
GFunctional
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, R
SS
, and
C
SS
.
T=-Css x Rss x ln((Vcont-1.55)/Vcont)
Example: When Css=0.1µF,Rss=470kΩ, and Vcont=5V, T=-0.1e
-6
×
470e
3
×
In((5-1.55)/5)=17.44ms.
CE/SS pin
Rss
Vcont
Css
〔Inside the IC〕
CE,
UVLO
To Verr amplifier
Vref circuit
Set the soft start time to a value sufficiently longer than the period of a clock pulse.
5
> Circuit example 1: N-ch open drain
Vcont
Rss
〔Inside the IC〕
CE/SS pin
ON/OFF signal
Css
> Circuit example 2: CMOS logic (low current dissipation)
Vcont
Rss
ON/OFF signal
Css
〔Inside the IC〕
CE/SS pin
> Circuit example 3: CMOS logic (low current dissipation), quick off
Vcont
Rss
ON/OFF signal
Css
〔Inside the IC〕
CE/SS pin
546
TOREX [ TOREX SEMICONDUCTOR ]
