LTC3632 LINER [Linear Technology], LTC3632 Datasheet - Page 9

• Manufacturer Part Number: LTC3632
• Description: High Effi ciency, High Voltage 20mA Synchronous Step-Down Converter
• Manufacturer: LINER [Linear Technology]

OPERATION
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
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
pin to ground. The 1μA current sourced out of this pin
(Refer to Block Diagram)
SET
pin to
SET
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
(4.35V maximum), an undervoltage detector disables
switching. Similarly, if V
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.
IN
rises above 55V typical (53V
IN
falls below 4V typical
LTC3632
3632fb
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