high side mosfet drivers

[boots_n_braces]

Hi all ive just orderd ac ouple of Internatinal rectifier half bridge drivers for an inverter project, ive not used anything similar before and ive noticed the schematics for using these (and most similar products) shows a capacitor connected between Vb (boost input) and Vs (source die connection) but no reference to sizing it? Im guessing that its size effects how far above source voltage the gate drive is but any ideas on the formulae?

Also is there a limit to the duty cycles they can (just generally) be run at? i.e do the usual upper and lower limits apply like most bootstrap circuits?

Thanks
Harry

 

[(*steve*)]

perhaps you can tell us what the device is that you bought, link t the datasheet, show us a schematic of (at least part of) your driving circuit, and describe your load.

You may also need to tell us what you're doing to ensure dead time if that's not obvious.

Without that stuff, it's hard to give information that is accurate.