MOSFET driving

[yashrk]

Hey guys  ,
     I was just seeing multiple videos on MOSFET  switching and many of them where emphasising on keeping stable ground connection and keep the switching part (N- channel with driver or P- channel) on the high side. Non of them where clear about why they prefer the high side switching over the low side switching.

     In what type of situations or circuits should I be concern about low side switching ?? 

[Simon]

Low side switching is easier as everything is referenced to ground but it means that you disconnect your loads ground which is not always possible. High side switching gets around this but the gate voltage is then referenced to the positive supply so it's hard when say you have a 12V circuit with a 3.3V control to control a gate that is at 12V when off and 9V when on. Level transitioning is required.

[yashrk]

Ohk so if its possible to switch the load using ground (which in my case is possible as its just a battery charger circuit) then I should go for it and it doesn’t have any other problem right ?

And if there is need of N- channel in high side what kind of ICs or bootstrap circuit do you prefer (battery is of 12V hence the gate voltage won't go too high) 

[Simon]

You can use N or P channel for highside, P is easier but N channel mosfets are cheaper for big ones and have better specs so if it is a lot of power it makes sense to have the bootstrap circuit and the N channel on a highside.

[yashrk]

Thank you for the reply but just want to know what types of bootstrap circuit do you prefer or which ICs (easily available) are used ?

[PSR B1257]

Depends of how you want to switch the MOSFET.
For PWM (duty cycle from 0.1 to 0.9 or there about and not too low frequencies) operation a usual bootstrap circuit will work.
For static switching (i.e. DC=1 or low switching frequencies) you need an auxilary pule generator, which is charging the boot strap capacitor.
You can build up such a circuit with a NE555 or use an IC like http://www.intersil.com/content/dam/Intersil/documents/isl6/isl6801.pdf