XC9220/XC9221
Series
■OPERATIONAL
EXPLANATION (Continued)
<U.V.L.O. (Under Voltage Lock Out) >
When the input voltage becomes 2.3V (TYP.) or lower, the external P-channel driver transistor is forced OFF. Once
the U.V.L.O. operates, the XC9220/XC9221A and C series (soft-start internally set type) resets the internal circuit. For
this, by releasing the U.V.L.O. function, the IC performs the soft-start function to initiate output startup operation.
When the input voltage falls because of a power cutoff etc. and the IC stops operation due to the U.V.L.O. function, the
IC resumes its operation by internal soft-start circuit of the XC9220/XC9221B and D series. If the soft-start time is
needed to set externally, the CE/C
SS
pin voltage should be reset to 0V. (Please see the soft-start circuit example.)
●U.V.L.O.
Operation
U.V .L.O. operation
VIN
U.V.L.O. ( Internal Signal)
VOUT
(XC9220/21A and C series)
VOUT
(XC9220/21B and D series)
U.V .L.O.
release delay
Sof t-start time: Tss1
Sof t-start time (Externally set-up) :Tss2
U.V .L.O.
release delay
Sof t-start time:Tss1
<Soft-Start Time>
The XC9220/XC9221B and D series can adjust the soft-start time externally via the CE pin. The soft-start function
operates until the CE pin voltage becomes 2.6V. Please refer to the following equation for calculating the soft-start
time. Minimum soft-start time is equal to the time set internally.
T
SS
= - C
SS
x R
SS
x In { (V
CE
– 2.2) / V
CE
}
Internal
sotf-starttime:Tss1
(XC9220/21A series)
XC9220/21A series
CE/CSS PIN
VCE
Css
XC9220/21B series
Minimum soft-start time
when externally set:
Tss2_min = Tss1
Externally set
soft-start time: Tss2
(XC9220/21A series)
Rss
> Circuit Example1 : N-ch Open Drain
VCE
> Circuit Examle2 : CMOS logic (low current dissipation) > Cicuit Examle3 : CMOS logic (low current dissipation, quick off)
VCE
Rss
ON/OFF
Signal
ON/OFF
Signal
Css
CE/CSS
PIN
Css
Rss
CE/CSS
PIN
ON/OFF
Signal
VCE
Rss
CE/CSS
PIN
Css
7/22
TOREX [ TOREX SEMICONDUCTOR ]
