high side mosfet driver

[tekman1]

Hi I would like to use a mosfet driver to enable the high side of a H bridge.

the driver vdd max ~18v the input is 3.3v logic, it should swing from 0 to vdd-.025mv

the supply voltage of the h bridge is applied to vdd.

Provide that I meet the gate turn on requirerment, would this turn on the highside?
I noticed that some devices are label high side, but in my situation they can be used for high or low is this true?

thanks pwr

 

[BradtheRad]

1.

Can you be sure 3.3V will fully turn on your mosfet? There may be mosfets whose gates are designed for that, I don't know. But the ones I've used need something like 5 or 10V to drive the mosfet to its maximum conductance.

2.

The gate V is referenced to the more positive or more negative terminal, depending on whether it's N-channel or P-channel.

If you use an N-channel in the high side, then you need to guarantee the source (negative) terminal will see a clear path to ground.

Will there be a motor and another mosfet intervening? Then consider using P-channel devices in the high side. Then the gate will be referenced to the drain (positive) terminal. It will see a clear path to V+.

Either that, or boost the volt level at the gate of the N-channel device high enough to guarantee it will turn on.