XCL222 Datasheet, PDF (9/20 Pages) Torex Semiconductor – 0.5A Inductor Built-in Step-Down “micro DC/DC” Converters

XCL221/XCL222
Series
■OPERATIONAL EXPLANATION (Continued)
<CL High Speed Discharge>
The product can quickly discharge the electric charge at the output capacitor (CL) when a low signal to the CE pin which
enables a whole IC circuit put into OFF state, is inputted via the N-ch MOS switch transistor located between the VOUT pin and
the GND pin. When the IC is disabled, electric charge at the output capacitor (CL) is quickly discharged so that it may avoid
application malfunction.
Output Voltage Dischage characteristics
V=VOUT(T) × e ^{- t / τ}
t =τLn (VOUT(T) / V)
R_DCHG=210Ω (TYP.) C_L=10μF
5.0
4.5
V : Output voltage after discharge
4.0
VOUT(T) : Output voltage
3.5
t : Discharge time
3.0
τ: CL×RDCHG
2.5
CL : Capacitance of Output capacitor
2.0
1.5
RDCHG : CL auto-discharge resistance,
1.0
but it depends on supply voltage.
0.5
0.0
Vout=1.2V
Vout=1.8V
Vout=3.3V
0 2 4 6 8 10 12 14 16 18 20
Discharge Time: t(ms)
<Current Limit>
The current limiter circuit of the XCL221/XCL222 series monitors the current flowing through the P-channel MOS driver
transistor connected to the Lx pin. When the driver current is greater than a specific level, the current limit function operates to
turn off the pulses from the Lx pin at any given timing. When the over current state is eliminated, the IC resumes its normal
operation.
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