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7.3 Soft-Start
When the POR function initiates the digital soft-start sequence, PWM error amplifier reference inputs are forced to track a voltage
level proportional to the soft-start voltage. As the soft-start voltage slews up, the PWM comparator regulates the output relative to
the tracked soft-start voltage, and slowly charges the output capacitor(s). In the digital soft-start sequence initiated by the POR
function, the soft start function is used to prevent surge current from power supply input during power on. The soft start duration
is 3mS in typical case.
VCC = 12V
12V
6V
0V
VCC = 5V
VOUT
TIME
3mS
Figure 3 : Soft start duration
7.4 Over-current Protection
To sense the low-side MOSFET’s RDS (ON) to set over-current trip point. Connecting a resistor (ROCSET) from this pin to PHASE
to set the over-current trip point, ROCSET, an internal 40μA current source, and the lower MOSFET on resistance, RDS (ON), sets
the converter over-current trip point (IOCSET) according to the following equation:
7.5 Under-voltage Protection
If the FB voltage drops under 0.5V, a fault signal is generated. When under voltage condition occurs, it will keep hiccup mode in
this event.
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V0.23P
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