Hi,

I have a MCU with +3.3V output pins, I will need to power down a device which expects -3.3V signal (it takes no more than 0.5mA current from this signal, it only expectes the negative voltage level).



How could I accomplish this? should I use a P-channel MOSFET, N-Channel? JFET? do you have a recommendation for a +3.3V logic level transistor?

Thank you very much in advance!
Andrea

 

hi 91,
A P MOSFET usually requires a negative Gate to Source control voltage.
E

 

The circuit below assumes that a 10k resistor to -3.3V will activate the power down signal. Note that the power down signal will be activated when the MCU output is low which is the reverse of your circuit.

 

Thank you for such fast answers. So I understand I should use n-Mosfet or BJT. Thank you AlbertHall for your schematic, the simulation looks good.

Another issue I have is that I should reduce to the minimum the power consumption. How ist it BJT vs N-Mosfet? which one would be better for power efficiency?
Thank you very much again for your help.
Andrea