N-MOS voltage drop at DS

Thread Starter

kemuelgersonb

Joined Mar 18, 2019
17
Hi,

Just want to ask is it normal to have a high voltage drop across drain and source of the n-mos?
The VBAT node is at 3.6V while the VDD_MAIN node is at 2.7V. Gate voltage is at 3.37V.

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dl324

Joined Mar 30, 2015
11,839
No. The circuit is intended to switch the VBAT to VDD_MAIN. But I did not consider the voltage drop of N-MOS. How to compensate it so I will have exactly 3.6V at VDD_MAIN?
Then you want to use a P channel MOSFET and ground the gate when you want the transistor turned on.
 

dl324

Joined Mar 30, 2015
11,839
But I will not be able to use the Magnetic on switch then as to trigger the VBAT to VDD? and redirect the magnetic on output to IC.
You can't use an N MOSFET to do what you want. That would require a sufficiently large Vgs to turn the device on and have a low on resistance.
 

Thread Starter

kemuelgersonb

Joined Mar 18, 2019
17
You can't use an N MOSFET to do what you want. That would require a sufficiently large Vgs to turn the device on and have a low on resistance.
Hi Dennis,

Thanks for the info. So I have to revise my design then. Or use just use buck converter instead.
 
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