I want to use MOSFET-N (MTM232270LBF) as a power switch for several ICs in my project. It should poweron the devices when logic level is high (3.3V) and poweroff when 0V.
I want to ask you if everything is ok with the design presented below.
Especially am I right if the MOSFET-N will work in saturation zone?
Some of the ICs will be connected to uC through SPI, UART, I2C. Everything will be ok when I shutdown the power?
Do I even need R2 resistor or I can connect uC directly?
I want to power the OPAMP for PT1000 temperature signal and the ground will have 0.003V offset from "real" ground. Should I consider this in error calculation for the PT1000 temperature?
simulate this circuit – Schematic created using CircuitLab
Best Answer
No, IRF7413 can not work from 3.3 V. Its max threshold voltage is 3 V. It means it just starts conducting at 2-3 V. The datasheet recommends to drive it by 10 V.
Furthermore, it is a switching MOSFET. Its gate resistor must be small (few Ohms). Most likely, it starts oscillations when driven like this.
And the most important question: do your ICs (I2C TEMP...) have a separate ground from the microcontroller?! The present design breaks GND connection. It is wrong for most cases.
You should use P channel MOSFET with logical level drive for this type of design. It is placed in 3.3 V supply line. The GND wire is common for microcontroller and all devices.