LTC3632_15 Datasheet, PDF (9/22 Pages) Linear Technology – High Efficiency, High Voltage 20mA Synchronous Step-Down Converter

LTC3632
OPERATION (Refer to Block Diagram)
on the SS pin instead. The internal and external soft-start
functions are reset on start-up and after an 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 10mA during its 0.75ms 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 pro-
vides a peak inductor current of 50mA. 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.
Input Undervoltage and Overvoltage Lockout
The LTC3632 implements a protection feature which dis-
ables switching when the input voltage is not within the
4.5V to 50V operating range. If V_IN falls below 4V typical
(4.35V maximum), an undervoltage detector disables
switching. Similarly, if V_IN rises above 55V typical (53V
minimum), an overvoltage detector disables switching.
When switching is disabled, the LTC3632 can safely sustain
input voltages up to the absolute maximum rating of 60V.
Switching is enabled when the input voltage returns to the
4.5V to 50V operating range.
3632fc
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