XC9119D10A
Series
■OPERATIONAL
EXPLANATION
<CE/SS (Pin No. 4): Chip Enable / Soft-Start Pin>
Pin No. 4 can be used as in either chip enable (CE) pin or soft-start (SS) pin. The IC takes about 5mS at most to attain the
setting voltage after starting operation (CE ‘H’) even though the R
SS
is 0Ω and the C
SS
is not connected.
Soft-start function is good for setting a longer time than the start-up time when the R
SS
is 0Ω and the C
SS
is not connected.
Soft-start operates while the CE pin voltage increases from 0V to around 1.9V. The following equation is used with the values of
Vcont voltage, the R
SS
and the C
SS
.
T = C
SS
x R
SS
x In {(Vcont – 1.6) / Vcont}
●Start-up
waveform
when the R
SS
is 0Ω and the C
SS
is not connected
R
SS
=0Ω, No C
SS
, V
IN
=3.6V, V
OUT
=15V, I
OUT
=3mA
1ch: V
OUT
0V (1ch)
⇒
0V (2ch)
⇒
2ch: CE
Time:500uS/div.
1ch:5V/div., 2ch:2V/div.
Ex.) When C
SS
=0.1uF, R
SS
=220kΩ, Vcont=5V,
T= - 0.1e – 6 x 220e3 x In{(5-1.6)/5} = 33.94mS
R
SS
CE/SS Pin
CE
C
SS
Vref
Error Amp.
Vcont
Ex.) Reference Circuit 1: N-ch Open Drain
Vcont
ON/OFF
Signal
R
SS
C
SS
CE/SS Pin
Ex.) Reference Circuit 2: CMOS Logic (Low Supply Current)
Vcont
ON/OFF
Signal
R
SS
C
SS
CE/SS Pin
Ex.) Reference Circuit 3: CMOS Logic (Low Supply Current), Quick-Off
Vcont
R
SS
CE/SS Pin
ON/OFF
Signal
C
SS
8
TOREX [ TOREX SEMICONDUCTOR ]
