XC6221
Series
■OPERATIONAL
EXPLANATION
<Output Voltage Control>
The voltage divided by resistors R1 & R2 is compared with the internal reference voltage by the error amplifier. The
P-channel MOSFET connected to the V
OUT
pin, is then driven by the subsequent output signal. The output voltage at the
V
OUT
pin is controlled & stabilized by a system of negative feedback. The current limit circuit and short protect circuit
operate in relation to the level of output current. Further, the IC's internal circuitry can be shutdown via the CE pin's signal.
CE
ON/OFF
Control
V
IN
-
CE
CE/
Error
Amp
Current
Limit
+
each
circuit
R1
Rdischg
V
OUT
CE/
R2
Voltage
Reference
V
SS
<Input and Output Capacitors>
The XC6221 needs an output capacitor C
L
for phase compensation. Values required for the phase compensation are
shown in the chart below. If a loss of the capacitance happens, the stable phase compensation may not be obtained.
Please ensure to use a capacitor which does not depend on bias or temperature too much. For a stable power input,
please connect an input capacitor C
IN
of 1.0μF between the V
IN
pin and the V
SS
pin.
●Except
USPN-4
OUTPUT VOLTAGE (V)
0.8V�½�1.15V
1.2V�½�1.35V
1.4V�½�4.0V
4.05V�½�5.0V
●USPN-4
OUTPUT VOLTAGE (V)
1.2V�½�4.0V
4.05V�½�5.0V
OUTPUT CAPACITOR VALUE
C
L
C
L
C
L
C
L
≧4.7μF
≧2.2μF
≧1.0μF
≧2.2μF
OUTPUT CAPACITOR VALUE
C
L
≧2.2μF
CL ≧4.7μF
<C
L
Auto-Discharge Function>
XC6221B/D series can discharge the electric charge in the output capacitor (C
L
), when a low signal to the CE pin, which
enables the whole IC circuit to be turned off, is inputted via the N-channel transistor located between the V
OUT
pin and
the V
SS
pin (cf. BLOCK DIAGRAM). The CL auto-discharge resistance value is set at 780Ω(V
OUT
=4.0V @ V
IN
=6.0V at
typical). The discharge time of the output capacitor (C
L
) is set by the CL auto-discharge resistance (R) and the output
capacitor (C
L
). By setting the time constant of the C
L
auto-discharge resistance value [R
DCHG
] and the output capacitor
value (C
L
) as
τ(τ=C
x R
DCHG
), the output voltage after discharge via the N-channel transistor is calculated by the
following formula.
–t/
V = V
OUT(E)
x e
τ
, or t=
τ
In ( V / V
OUT(E)
)
where
V : Output voltage after discharge
V
OUT (E)
: Output voltage
t : Discharge time
τ:
C
L
auto-discharge resistance R
DCHG
×Output
capacitor (C
L
) value C)
8/23
TOREX [ TOREX SEMICONDUCTOR ]
