XC8108_15 Datasheet, PDF (9/25 Pages) Torex Semiconductor – High Function Power Switch

■OPERATIONAL EXPLANATION
XC8108
Series
The XC8108 series is a P-channel MOSFET power switch IC.
The XC8108 series consists of a CE circuit, UVLO circuit, thermal shutdown circuit, current limiter circuit, reverse current
prevention circuit, control block and others. The gate voltage of the power switch transistor is controlled with control block.
The current limiter circuit and reverse current prevention circuit will operate based on the output voltage and output current.
(See the BLOCK DIAGRAM below)
BLOCK DIAGRAM (XC8108 Series)
<CE Pin>
The voltage level which is fed to CE pin controls the status of this IC. If either “H” level or “L” level which is defined as the
electrical specification is fed to CE pin, then XC8108 can operate in standard manner. However, if the middle voltage which is
neither “H” level nor “L” level is fed to CE pin, the consumption current will increase due to the shoot-through current at internal
circuits. Also if CE pin is open, the status of XC8108 cannot be fixed and the behavior will be unstable.
<Thermal Shutdown>
For protection against heat damage of the ICs, thermal shutdown function is built in. When the internal junction temperature
reaches the temperature limit, the thermal shutdown circuit operates and the power switch transistor will turn OFF. The IC
resumes its operation when the thermal shutdown function is released and the IC’s operation is automatically restored because
the junction temperature drops to the level of the thermal shutdown release temperature. When the thermal shutdown circuit
detects higher junction temperature than the detect temperature, the voltage level of FLG pin is low level. When the thermal
shutdown circuit detects lower junction temperature than the release temperature, the thermal shutdown function is released
and the voltage level of FLG pin is high level.
<Under Voltage Lockout (UVLO) >
When the V_IN pin voltage goes down to lower voltage than UVLO detected voltage, the power switch transistor turns OFF by
UVLO function in order to prevent false output caused by unstable operation of the internal circuitry. When the V_IN pin voltage
goes up to higher voltage than UVLO released voltage, the UVLO function is released and the power switch transistor can turn
ON.
<Soft-start Function>
The soft-start circuit can reduce the in-rush current charged on the output capacitor when IC starts up. Additionally, due to the
reduction of the in-rush current, the circuit can reduce the fluctuation of the input voltage as well. The soft-start time is optimized
internally and defined as turn-on time. (TYP: 0.6ms)
9/25