XC8102
Series
■OPERATIONAL
EXPLANATION
<CE Pin>
The XC8102 enables an output P-channel MOSFET switch and the IC internal circuitry to turn off by the signal to the CE pin. In
the shutdown mode, the V
OUT
pin will be pulled down to the V
SS
by the C
L
auto-discharge function.
The output voltage becomes unstable when the CE pin is opened. If the input voltage to the CE pin is within the specified
threshold voltages, the logic is fixed and the XC8102 will operate normally. However, supply current may increase as a result
of the shoot-through current of internal circuitry when the medium level voltage is input to the CE pin.
＜Input/Output
Capacitor＞
The XC8102 works well without an input and output capacitors. Also, an output capacitor of the power source can be used as
an input capacitor of the XC8102 and a bypass capacitor of the driving IC can be used as an output capacitor of the XC8102.
<CL Auto-Discharge Function>
The XC8102AA contains a C
L
auto-discharge resistor and an N-channel transistor between the V
OUT
pin and the V
SS
pin. The
device quickly discharge the electric charge in the output capacitor (C
L
) when a low signal to the CE pin is input to turn off a
whole IC circuit. The C
L
auto-discharge resistance is set at 480Ω (V
OUT
=4.0V TYP. @ V
IN
=4.0). Discharge time of the
output capacitor (C
L
) is determined by a CL auto-discharge resistor value (Rdischg) and an output capacitor value. Time
constant
τ
is defined as (τ = C x Rdischg). Output voltage after starting discharge can be calculated by the following
formula.
V = V
OUT
x e
–t/
τ
,
or
t=τIn (V
OUT
/ V)
V: Output voltage after starting discharge,
V
OUT:
Output voltage,
t : Discharge time,
τ:
Output discharge resistor value Rdischg×Output capacitor (C
L
) value C
<Current Limiter, Short-Circuit Protection>
The XC8102 series contains a constant current limiter and fold-back current circuitry. The constant current limiter operates to
limit output current and the fold-back current circuitry operates as short circuit protection for the output pin.
When the load current reaches the limit current, the constant current limiter operates and the output voltage drops. The output
voltage further, then the fold-back current circuitry operates to decrease the output current. When the output pin is
short-circuited to the ground, the output current drops and maintains a flow about 30mA.
■NOTES
ON USE
1.
2.
3.
4.
Please use this IC within the stated absolute maximum ratings. Operation beyond these limits may cause degrading or
permanent damage to the device.
The X8102 goes into an undefined operation when the CE pin is left open. The CE pin shall be tied to low or high level.
V
OUT
pin voltage should not be applied beyond the V
IN
pin voltage.
The IC may get damage due to the reverse current toward the V
IN
pin.
Current limit function is integrated. However, power dissipation may be beyond the limit before starting a fold-back current
protection when used in high temperature. For the power dissipation of each package, please refer to the graphs of Package
Power vs. Operating Temperature in page 15 to 17.
7/18
TOREX [ TOREX SEMICONDUCTOR ]
