TPS55340: How to fix Css capacitor value ?

Part Number: TPS55340

Hi, 

At the startup of the TPS55340 there is a current peak that I'd like to get rid off. Accordinf to the Datasheet it can be modulated by the Css capacitor. It is already fixed at 0.22µF but it appears to be inadequate. Is there any formula to set the capacitor value ? 

Thanks, 

Alexandre