XCL211 datasheet(8/16 Pages) TOREX

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XCL211/XCL212 series

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

1012

1618

Discharge Time: t(ms)

VOUT = 1.2V

VOUT = 1.8V

VOUT = 3.3V

Output Voltage Dischage characteristics

Rdischg = 130Ω(TYP.)

OUT =1.2V

OUT =1.8V

OUT =3.3V

L=20μF

■

OPERATIONAL DESCRIPTION (Continued)

For protection against heat damage, the thermal shutdown function monitors chip temperature. When the chip’s temperature reaches 150OC

(TYP.), the thermal shutdown circuit starts operating and the P-channel driver transistor will be turned off. At the same time, the output voltage

decreases. When the temperature drops to 130OC (TYP.) after shutting off the current flow, the IC performs the soft start function to initiate

output startup operation.

< Function of CE pin >

The XCL211/212 series will enter into stand-by mode by inputting a low level signal to the CE pin. During a stand-by mode, the current

consumption of the IC becomes 0μA (TYP.). The IC starts its operation by inputting a high level signal to the CE pin. The input of the CE pin is

a CMOS input and the sink current is 0μA (TYP.).

<UVLO>

When the VIN pin voltage becomes 2.4V (TYP.) or lower, the P-channel MOS driver transistor output driver transistor is forced OFF to prevent

false pulse output caused by unstable operation of the internal circuitry. When the VIN pin voltage becomes 2.68V (MAX.) or higher, switching

operation takes place. By releasing the UVLO function, the IC performs the soft start function to initiate output startup operation. The soft start

function operates even when the VIN pin voltage falls momentarily below the UVLO operating voltage. The UVLO circuit does not cause a

complete shutdown of the IC, but causes pulse output to be suspended; therefore, the internal circuitry remains in operation.

The XCL211/XCL212 series provide 1.0ms (TYP). Soft start time is defined as the time interval to reach 90% of the output voltage from the time

when the VCE is turned on.

The XCL211/XCL212 series 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-channel MOS switch transistor located between the LX pin and the VGND pin.

When the IC is disabled, electric charge at the output capacitor (CL) is quickly discharged so that it may avoid application malfunction. 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 [R] and an output capacitor value (CL) as τ(τ=C x R), discharge time of the output voltage after discharge via

the N-channel transistor is calculated by the following formulas.

V = VOUT(E)×e -t /τ or t = τln (VOUT(E) /V)

V : Output voltage after discharge

VOUT(E) : Output voltage

t: Discharge time

: CL×RDCHG

CL : Capacitance of Output capacitor

RDCHG : CL auto-discharge resistance

RDCHG

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