LM3679

SNVS510A – SEPTEMBER 2007 – REVISED FEBRUARY 2008

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SOFT START

The LM3679 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

2.5V. Soft start is implemented by increasing switch current limit in steps of 200mA, 400mA, 600mA and 920mA

(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 350mA load is 300 µs and with

1mA load is 200µs.

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