XC8107 Series
■OPERATIONAL EXPLANATION (Continued)
<Current limiter, short-circuit protection>
When the output current reaches the current limit value, the constant current limiter circuit activates and as a result, the
output voltage goes down.
If the short circuit comes at the VOUT pin, the output current is limited to the current which is specified as the short-circuit current
value. If the over-current state lasts for 7.5ms (TYP.), the FLG pin changes to Low level output.
Two types are available for the current limiter circuit: an auto recovery type (product type C) and a latch off type (product type
D). After the current limiter circuit activates and the FLG pin outputs low level, the operation is different between these two
types.
The auto recovery type continuously limits the output current by the current limit value.
When the over-current status finishes and the status of that the output current is less than the current limit value continues for
7.5ms (TYP.) or more, the voltage of FLG pin goes up “H” level again.
The latch off type turns off the power switch transistor after the FLG pin outputs Low level. The off state is maintained
regardless of whether the over-current state is released.
Latch operation is released by turning off the IC with the CE pin signal and then restarting, or by lowering the input voltage
below the UVLO detected voltage once and after that raising it higher than UVLO released voltage.
<Reverse current prevention>
An internal circuit is built in that prevents reverse current from the VOUT pin to the VIN pin.
When the difference between input voltage and VOUT pin voltage is higher than the detect voltage set internally, the reverse
current prevention circuit activates, and the power switch transistor turns off, then the reverse current from the VOUT pin to the
VIN pin is reduced to 0.1μA (TYP.).
If the reverse-voltage state lasts for 4ms (TYP.), the FLG pin changes to Low level output.
Two types are available for the reverse current prevention circuit: the auto recovery type (product type C) and the latch off
type (product type D). After the reverse current prevention circuit activates and the FLG pin outputs low level, the operation is
different between these two types.
On the auto recovery type, when the output voltage drops below the input voltage, the reverse current prevention circuit stops
immediately, and the power switch transistor turns on again. If the output voltage remains lower than the input voltage for 4ms
(TYP.), the FLG pin returns to High level output.
On the latch off type, the power switch transistor remains in the off state even if the reverse voltage state is released.
Latch operation is released by turning off the IC with the CE pin signal and then restarting, or by lowering the input voltage
below the UVLO detected voltage once and after that raising it higher than UVLO released voltage.
10/27
TOREX [ Torex Semiconductor ]
