XC6221A252MR-G Datasheet, PDF (8/28 Pages) Torex Semiconductor – Low ESR Caps Compatible High Speed LDO Voltage Regulator with ON/OFF Switch

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
CE
CE/
each
circuit
-
Error
Amp
+
Current
Limit
V IN
R1 Rdischg
CE/
V OUT
Voltage
Reference
R2
VSS
<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)
0.80V～1.15V
1.20V～1.35V
1.40V～4.00V
4.05V～5.00V
OUTPUT CAPACITOR VALUE
C_L ≧4.7μF
C_L ≧2.2μF
C_L ≧1.0μF
C_L ≧2.2μF
●USPN-4
OUTPUT VOLTAGE (V)
1.20V～4.00V
4.05V～5.00V
OUTPUT CAPACITOR VALUE
C_L ≧2.2μF
C_L ≧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 and C_L auto-discharge resistance
(R_DCHG) located between the V_OUT pin and the V_SS pin (cf. BLOCK DIAGRAM). The C_L auto-discharge resistance (R_DCHG)
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 C_L
auto-discharge resistance (R_DCHG) 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_L x R_DCHG), the output voltage after discharge via
the N-channel transistor is calculated by the following formula.
V = V_OUT(E) x e ^–t/τ, or t=τIn ( 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 value C_L
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