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High side Charge pump supplies

Category: Datasheet/Specs

I am building a multi-MHz buck converter for envelope tracking and am trying to take an alternate route for powering the high side FET other than a bootstrap diode.  I run into the issue that at high duty cycles the bootstrap capacitor does not have enough time to charge up.  I understand that some people use isolated power supplies, for instance a fly back, but those are bulky.  Are there such things as isolated or split ground charge pump converters?  I saw there was MAX1822 that seems similar to what I was looking for.  I am using GAN so would only need an isolated 5V.  My input voltage to the buck converter would ideally be 55V, but can use 40V if that offers more opportunities.  Any Advice/Guidance is much appreciated.