Hi to all.
Hoping someone can help out.
In the datasheet for the LM2840 there are a couple of Application ccts , starting on page 9. I'd like to know how these inductor values are calculated , especially the one
in figure 2. With a 42V input and a 3.3V output the 15uH is no where near big enough to fulfill the 30% ripple current requirement. Well it not actually a requirement , more a rule of thumb , but it's not an unreasonable value.
Ignoring diode drop the peak to peak ripple current with 100mA load is over 400mA! , that's with 15uH. Even at 1.5Mhz this requirement won't be met , not even close.
I'd be using at least 100uH.
Am I missing something here? Is there some design requirement that I've overlooked.
Cheers
Robin