XC6221 Datasheet, PDF (9/20 Pages) Torex Semiconductor – Low ESR Caps Compatible High Speed LDO Voltage Regulators 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, which is connected to the VOUT pin, is then driven by the subsequent output signal. The output
voltage at the VOUT 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.
<Low ESR capacitor>
With the XC6221 series, a stable output voltage is achievable even if used with low ESR capacitors, as a phase
compensation circuit is built-in. Values required for the phase compensation are as the chart below. In order to ensure the
stable phase compensation while avoiding run-out of values, please use the capacitor, which does not depend on bias or
temperature too much. For a stable power input, please connect an input capacitor (CIN) of 1.0μF between the VIN pin and
the VSS pin.
SETTING OUTPUT VOLTAGE (V)
0.8 ~ 1.15
1.2 ~ 1.35
1.4 ~ 4.0
OUTPUT CAPACITOR VALUE
CL=4.7uF
CL=2.2uF
CL=1.0uF
<CL Auto-Discharge Function>
XC6221B series can discharge the electric charge in the output capacitor (CL), when a low signal to the CE pin, which
enables a whole IC circuit turn off, is inputted via the N-channel transistor located between the VOUT pin and the VSS pin
(cf. BLOCK DIAGRAM). The CL auto-discharge resistance value is set at 780Ω(VOUT=4.0V @ VIN=6.0V at typical).
The discharge time of the output capacitor (CL) is set by the CL auto-discharge resistance (R) and the output capacitor
(CL). By setting time constant of a CL auto-discharge resistance value [Rdischg] and an output capacitor value (CL) as τ
(τ=C x Rdischg), the output voltage after discharge via the N-channel transistor is calculated by the following formulas.
V = VOUT(E) x e ^–t/τ, or t=τIn ( V / VOUT(E) )
( V : Output voltage after discharge, VOUT(E) : Output voltage, t: Discharge time,
τ: CL auto-discharge resistance Rdischg×Output capacitor (CL) value C)
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