AT1380A Datasheet, PDF (8/12 Pages) Aimtron Technology – Switching Regulator Controller for LCD Bias

Functional Description
Soft Start SCP
AT1380A
Preliminary Product Information
Switching Regulator Controller for LCD Bias
Figure 1. Soft-Start SCP circuit
At power-on, the AT1380A enters the soft-start mode to prevent current spike and overshoot. The
capacitor CS is charged from 0V at a constant current of 1µA.
The soft-start time for the duty cycle
t_S = 0.8 × CS(µF )
When V_SCP reaches 0.8V, the AT1380A leaves the soft-start mode to enter the normal mode and enable
the SCP function. If the output load conditions change rapidly causing the output to drop suddenly, the
external capacitor CS will start to charge because the error amplifier output (FB pin) is fixed at V_OM+.
When the external capacitor is charged above 0.8V, the output pin is set low. Once the latch circuit has
set, the capacitor CS will be discharged to low state and the latch circuit will not reset until power is
turned off or the power supply is restarted.
Short-circuit detection time (or full soft-start time) :
t_PE = 0.8 × CS(µF )
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
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