Datasheet LTC3632 (Analog Devices) - 9

LTC3632
OPERATION (Refer to Block Diagram)
on the SS pin instead. The internal and external soft-start through the resistor generates a voltage that is translated functions are reset on start-up and after an undervoltage into an offset in the peak current comparator, which limits or overvoltage event on the input supply. the peak inductor current. In order to ensure a smooth start-up transition in any
Input Undervoltage and Overvoltage Lockout
application, the internal soft-start also ramps the peak inductor current from 10mA during its 0.75ms ramp time The LTC3632 implements a protection feature which dis- to the set peak current threshold. The external ramp on ables switching when the input voltage is not within the the SS pin does not limit the peak inductor current during 4.5V to 50V operating range. If VIN falls below 4V typical start-up; however, placing a capacitor from the ISET pin to (4.35V maximum), an undervoltage detector disables ground does provide this capability. switching. Similarly, if VIN rises above 55V typical (53V minimum), an overvoltage detector disables switching.
Peak Inductor Current Programming
When switching is disabled, the LTC3632 can safely sustain The offset of the peak current comparator nominally pro- input voltages up to the absolute maximum rating of 60V. vides a peak inductor current of 50mA. This peak inductor Switching is enabled when the input voltage returns to the current can be adjusted by placing a resistor from the I 4.5V to 50V operating range. SET pin to ground. The 1µA current sourced out of this pin 3632fc 9 Document Outline FEATURES DESCRIPTION APPLICATIONS TYPICAL APPLICATION ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION ORDER INFORMATION ELECTRICAL CHARACTERISTICS TYPICAL PERFORMANCE CHARACTERISTICS PIN FUNCTIONS BLOCK DIAGRAM OPERATION APPLICATIONS INFORMATION TYPICAL APPLICATIONS PACKAGE DESCRIPTION REVISION HISTORY TYPICAL APPLICATION RELATED PARTS