LTC3642 Datasheet, PDF (9/20 Pages) Linear Technology – High Effi ciency, High Voltage 50mA Synchronous Step-Down Converter

LTC3642
OPERATION (Refer to Block Diagram)
on the SS pin instead. The internal and external soft-start
functions are reset on start-up and after undervoltage or
overvoltage event on the input supply.
In order to ensure a smooth start-up transition in any
application, the internal soft-start also ramps the peak
inductor current from 25mA during its 1ms ramp time to
the set peak current threshold. The external ramp on the
SS pin does not limit the peak inductor current during
start-up; however, placing a capacitor from the I_SET pin
to ground does provide this capability.
Peak Inductor Current Programming
The offset of the peak current comparator nominally
provides a peak inductor current of 115mA. This peak
inductor current can be adjusted by placing a resistor
from the I_SET pin to ground. The 1μA current sourced out
of this pin through the resistor generates a voltage that is
translated into an offset in the peak current comparator,
which limits the peak inductor current.
3642f
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