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XC9281/XC9282

Series

■OPERATIONAL EXPLANATION(Continued)

＜UVLO function＞

When the VIN voltage becomes 2.0V (TYP.) or less, the UVLO function operates to forcibly turn off the Pch MOS driver transistor

to prevent erroneous pulse output due to operation instability of the internal circuit. When the VIN voltage becomes 2.1V (TYP.) or

more, the UVLO function is canceled. After the UVLO function is canceled, the output voltage rises with the soft start function,

and then the normal operation is performed. Moreover, during the UVLO operation, the internal circuit is operating because

stopping by UVLO is not same to a standby mode and just switching operation is stopped.

＜CL Discharge function＞

B type can discharge in a fast manner the output capacitor by internal Nch MOS transistor connected to VOUT pin in order to

prevent malfunction of application due to charge remaining in output capacitor during standby. The output voltage during

discharging can be calculated by the following equation.

V = VOUT (T) × e -t /

τ

t =τLn (VOUT (T) / V)

V

: Output voltage during discharge

VOUT (T)

: Output voltage

t

: Discharge time

CL

: Effective capacitance of Output capacitor

RDCHG

: CL auto-discharge resistance

τ

: CL×RDCHG

Output Voltage Discharge characteristics

RDCHG =

145Ω (TYP.), CL=4.7μF

V

OUT (T)

= 1.0V

V

OUT (T)

= 1.8V

V

OUT (T)

= 3.3V