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OPERATIONAL EXPLANATION (Continued)

<Soft-start function>

The reference voltage applied to the error amplifier is restricted by the start-up voltage of the EN/SS pin. This ensures that the

error amplifier operates with its two inputs in balance, thereby preventing ON-time signal from becoming longer than necessary.

Therefore, start-up time of the EN/SS pin becomes the set-time of soft-start. The soft-start time can be adjusted by adding a

capacitor and a resistor to the EN/SS pin.

The soft-start function operates when the voltage at the EN/SS pin is between 0.3V to 2.5V. If the voltage at the EN/SS pin does

not start from 0V but from a middle level voltage when the power is switched on, the soft-start function will become ineffective and

the possibilities of large inrush currents and ripple voltages occurring will be increased.

<Thermal shutdown>

The thermal shutdown (TSD) as an over current limit is built in the XCL225/XCL226 series.

When the junction temperature reaches the detection temperature, the driver transistor is forcibly turned off. When the junction

temperature falls to the release temperature while in the output stop state, restart takes place by soft-start.

<UVLO>

soft-start function activates, and output start operation begins. Stopping by UVLO is not shutdown; only pulse output is stopped

<Power good>

The output state can be monitored using the power good function.

When the FB voltage drops below 90% (TYP.), the PG pin outputs an "L" signal.

The PG pin is an Nch open drain output, therefore a pull-up resistance (approx. 100kΩ) must be connected to the PG pin.

When not using power good function connect the PG pin to GND or open it for use.