I need to control with Arduino powered (necessarily) at 5V the power ON/OFF of a circuit that has 3.6V power supply.
Arduino needs to replace a physical switch that simply connects the 3.6 battery to the rest of the circuit.
I have seen a lot of examples but all uses a mosfet connected to the pin but with controlled Voltage higher than the output pin voltage. (i.e. 12V or 9V with an Arduino at 5V).
Cannot drive directly the load from the output port using a voltage level translator. Do you have any suggestion?
Best regards and thanks
Use a relay ?
Either low-side switch with a logic-level n-MOSFET (the output voltage can be smaller, same or higher than the controlling circuit)
Or use a logic-level p-MOSFET to high-side switch. If the gate is more positive than
the source on a p-FET it will still be very "off". The p-FET needs to cope with only
3.6V of drive, note, not all will, you'll probably only find surface-mount MOSFETs for
such low gate-drive voltages.
The NDP6020P is a TO-220 logic-level P-channel mosfet you could use. The GS threshold is 1V maximum, so at 3.6V it would be fully on.
Will the 5V supply and the 3.6V supply always be switched on and off together? If the 5V supply is off while the 3.6V supply is on, then the mosfet will turn on. If that's not acceptable, you would need to add a second stage "N" device ahead of the mosfet gate so the Arduino would have to output a high voltage to turn on the mosfet.
the 5V comes from the output of the Arduino pin that controls the Mosfet.
Cannot understand your statement when you say " will be the 5V and 3.6V always be switched ON/OFF together". Sorry. Could you please explain?
I'm talking about the 5V supply that powers the Arduino. If you use a P-channel mosfet as the switch, you'll have a circuit that looks something like the picture below. The Arduino will have to bring the mosfet gate high to turn it off. So if the power to the Arduino is ever turned off while the 3.6V supply is still active, the mosfet will turn on. So I'm asking if that could ever happen - whether the Arduino could ever be powered down while the 3.6V power is still active.
Thank You Sherman.
Nope the 5V rail is tied together with the 3.6V since the latest is obtained by a 1117 voltage regulator.
Such a case would never occur.
Really appreciate that.