AAT1109A Ver la hoja de datos (PDF) - Advanced Analogic Technologies

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Fabricante

AAT1109A

ONE-CHANNEL BOOST SWITCHING REGULATOR

Advanced Analogic Technologies 

Advanced Analog Technology, Inc.

AAT1109A

How to set the time constant for soft start and short circuit protection

1.Soft start

At power on, the AAT1109A operates in soft start mode. The capacitor Cscp connected to SCP pin starts

charging at a constant current. In the soft start mode, the voltage at SCP pin (VSCP) is input to the PWM

comparator, so that the ON duty of the OUT pin is controlled by the VSCP. On completion of soft start

operation, the voltage at the SCP pin stays low, the input from soft start circuit to the PWM comparator

stay high, and enter the short circuit protection waiting state.

Soft start time

Ts(sec) ~ 0.84 × CSCP (uF)

2.Short circuit protection

If the switching regulator output suddenly drops due to loading effect , the error amplifier output is fixed at

VOM+ and capacitor CSCP starts charging. When the voltage at the SCP pin reaches approximately 1.26V

,the output pin set low and SCP pin stays low.

Once the protection circuit operates, the circuit can be recovered by setting the power supply.

Short circuit detection time

Tscp(sec) ~ 0.84 × CSCP (uF)

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