PMOS Switch (high side switch)

Thread Starter

Qual

Joined Aug 5, 2016
48
Hi All,

I want to switch on / off a 1A load, so using P-Channel Mosfet and gate is connected to 3.3V MCU .

When MCU sends Gate = 1 Mosfet is OFF.
MCU sends Gate = 0 Mosfet ois ON.

Here source is connected to +5V so when GATE = 0 the load is suppose to be on and should get +5V and current flow of 1A to it.
i have doubt on switching on mosfet using MCU, ( Gate = 0) is there any thing i should take care.

VGS is suppose to be -ve , i am using only 5V, 3.3V

How i am suppose to select p chaneel mosfet with these requirement
 
Last edited:

AlbertHall

Joined Jun 4, 2014
10,915
The VGS will be -1.7V when the MOSFET should be off. That means that the minimum gate threshold voltage should be greater than or equal to 1.7V.

The VGS will be -5V when the MOSFET should be on. That means that the MOSFET should be able to pass 1A with very low VDS. Check the VGS at which RDSon is specified. If it is 5V or less it will do fine. If not that MOSFET still might be OK. You will need to check the performance graphs in the datasheet carefully.
 

crutschow

Joined Mar 14, 2008
26,402
It would be better if you added an NPN driver transistor to control the gate voltage.
That way the gate can go from 0V (fully ON) to 5V (fully OFF).
You still need a logic-level P-MOSFET that turns fully on at a Vgs of -5V.
 

Thread Starter

Qual

Joined Aug 5, 2016
48
It would be better if you added an NPN driver transistor to control the gate voltage.
That way the gate can go from 0V (fully ON) to 5V (fully OFF).
You still need a logic-level P-MOSFET that turns fully on at a Vgs of -5V.
Well i thought same but doubtful on choosing MOSFET:confused: as need to on/off load ( 5V , 1A) so prefer for high side.
 
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