Am I using the right P-channel MOSFET for my high side switch?

Thread Starter

Zurn

Joined Mar 4, 2019
73
Hi everyone,

I'm using a microcontroller to control power to my system with a p-channel MOSFET. The uC is an ATTiny85 and the MOSFET is an NDP6020P.

As of now my system is runs between 12 and 16V and everything works fine - however, when I charge the batteries everything jumps up to 24V. Could this be a problem for my MOSFET?

Here's my circuit:
P-Channel-MOSFET-Power-Switch.png
The load is a bunch of things: special uCs, voltage regulators, and some hydrophones.

I've had some problems in the past with misreading MOSFET data sheets, so I figured it would be wise to get a second opinion.
 

Alec_t

Joined Sep 17, 2013
10,746
The Absolute Maximum Vgs is given as ±8V for that FET. You are using Vgs = 24*10/15 = 16V. Also, maximum rated Vds is only -20V. Houston, I think you have a problem (or two)!
 

Thread Starter

Zurn

Joined Mar 4, 2019
73
The Absolute Maximum Vgs is given as ±8V for that FET. You are using Vgs = 24*10/15 = 16V. Also, maximum rated Vds is only -20V. Houston, I think you have a problem (or two)!
Ah yes, I accidentally swapped the resistors in my voltage divider calculation (I did 24*5/15 = 8V). I guess if I swap those resistors around I'll only have one problem.

Now to find a logic controlled P-MOSFET with a Vds of -24V...

Thanks for the input.
 

djsfantasi

Joined Apr 11, 2010
5,962
Ah yes, I accidentally swapped the resistors in my voltage divider calculation (I did 24*5/15 = 8V). I guess if I swap those resistors around I'll only have one problem.

Now to find a logic controlled P-MOSFET with a Vds of -24V...

Thanks for the input.
Or more. Perhaps one with a Vds of 30V would work? That’s what I used in a 12V system.
 
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