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WEBENCH® Tools/LM27402: Soft start time (tss)

Prodigy 10 points

Replies: 3

Views: 57

Part Number: LM27402

Tool/software: WEBENCH® Design Tools

Hi,

We are using the "LM27402" buck controller for converting Vin=3.3V to Vout=1V@10A. For this design, we need a soft start delay tss=5ms. For this delay, the WEBENCH is recommending to use a capacitor of Css=47nF. But as per the formula mentioned in the datasheet of "LM27402" if we substitute the value of Css=47nF,

tss=Css*0.6/Iss,
=> tss= 47nF*0.6/3uA,
=> tss= 9.4ms

So, can you please suggest which one is reliable. Our requirement is we need a soft start delay tss=5ms, can we take the WEBENCH simulation report capacitor value or we need to calculate it as per the datasheet. ?