Hi All,

I need to control one microprocessor board by another via a MOSFET switch. However, I can't seem to get the MOSFET to work! Here are the steps I followed:

uP board 1 sends a 3.3V signal to the MOSFET (nMOS) gate.
The Vcc pin of uP board 2 is connected to 3.3V.
All grounds of uP board are connected together, and connected to the drain of nMOS chip.
The source of MOSFET is connected to ground
Resistor of 100k is connected between gate and ground.

When the 3.3 power supply is switched on, the setup does not work!

Any help would be appreciated.

Thanks,
Talini

 

With no schematic, there is no way to see the error.

At a guess, you may not be using a logic level FET, so the 3.3 volts on the gate will not turn it on. If the second microprocessor is in the source circuit, the switching can't work, as the source voltage will be about equal to the gate.

You may have to think about using a reed relay to do the voltage switching - again a schematic would be helpful.

 

I don't think you can turn on even a logic level FET most are only good for 5 volts and google didn't turn up any at 3.3 volts

There this LTC1157 3.3V Dual Micropower
High-Side/Low-Side MOSFET Driver

http://www.google.com/url?sa=t&sour...0NmHBg&usg=AFQjCNEu-YzJXo_EELJaHMc4Py3PFvCFIA

There are some but finding one may be hard this is one http://www.irf.com/product-info/hi-rel/fs8307.pdf