high side n channel mosfet

[vini_i]

what is the advantage or disadvantage to using a high side n channel mosfet versus a high side p channel mosfet?

i'm working to make some changes to a small motor drive board. the only function of the board is to turn a small set of 3.3v motors on and off. the circuit i fully isolated from everything and is controlled using a opto isolator. the basic topology is; 24v is stepped down to 3.3v. then there are some filter and stiffening capacitors. then there is the n channel mosfet and then the out put to the motors. the mosfet is driven with a ltc1981 driver chip. the driver is pulled up and the opto pull it down.

if i was designing this circuit i would have used a p channel mosfet. the original designer is no longer around to ask. am i missing something? why would the original designer have used an n channel?

[BradC]

if i was designing this circuit i would have used a p channel mosfet. the original designer is no longer around to ask. am i missing something? why would the original designer have used an n channel?

Lower Rdson, cheaper, greater selection.

[Mechatrommer]

if i was designing this circuit i would have used a p channel mosfet. the original designer is no longer around to ask. am i missing something? why would the original designer have used an n channel?

Lower Rdson, cheaper, greater selection.

thats the pro. the con is you need the bootstrapper like the ltc1981.... p-mosfet is vice versa that.

[Jeroen3]

p-channels are somewhat more difficult to produce. And therefore more expensive.
Using an N-channel only requires a voltage booster, these are available in small IC's nowadays, so the threshold of getting high-side N switches is not as high.

You can even get smart high side switches (or powerpath controllers if <5V), which are basically n-channel and driver circuitry integrated. Infineon has as lot of these. They're nice because some have feedback circuitry and automotive specifications. Bit more expensive though. But nice as low current solid state relays.

Compare some n-channel with high-side driver combo's, versus p-channel fets. And see what suits the design best. Probably p-channel in your case. If you're not running a lot of amps.