LM3676

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SNVS426C – NOVEMBER 2006 – REVISED MAY 2013

SOFT START

The LM3676 has a soft-start circuit that limits in-rush current during start-up. During start-up the switch current

limit is increased in steps. Soft start is activated only if EN goes from logic low to logic high after Vin reaches

2.9V. Soft start is implemented by increasing switch current limit in steps of 70mA, 140mA, 280mA and 1020mA

(typical switch current limit). The start-up time thereby depends on the output capacitor and load current

demanded at start-up. Typical start-up times with a 10µF output capacitor and 300mA load is 400µs and with

1mA load is 275µs.

LDO - LOW DROP OUT OPERATION

The LM3676-ADJ can operate at 100% duty cycle (no switching; PMOS switch completely on) for low drop out

support of the output voltage. In this way the output voltage will be controlled down to the lowest possible input

voltage. When the device operates near 100% duty cycle, output voltage ripple is approximately 25 mV.

The minimum input voltage needed to support the output voltage is

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