Teency LC or 3.2 driving N- MOSFET : current limiting resistor + common ground

AlainD

Well-known member
Hi

A few questions about driving a MOSFET from the Teensy LC or 3.2
I've seen that the Teensy LC has a few output pins that can have a current of 20mA, the Teensy 3.2 is limited to 10mA.
On the other hand I's seen post that suggest a 150ohm current limiting resistor for driving a MOSFET with a Teensy 4.1 (with "The recommended maximum output current is 4mA").

What is a "safe" (for the Teensy) resistor value for driving a high "total gate charge" (24nC for the IRF3708) MOSFET?
Is it different for the LC (for those few 20mA pins) and a Teensy 3.2?

In an application I would start from 12V or 24V and power the Teensy from a DC-DC buck convertor (probably the TSR 0.5-2450 for 500mA 5V).
Can I consider the ground on the DC-DC as common (just to be sure)?

A suggestion for a less powerful logic level MOSFET (switching at most the 500mA 5V on the Vin)?
 
The current limits on the I/O pins is steady state so the pulsed current for driving a MOSFET is not a problem. You do want to put a resistor of 100 Ohms or so as close as possible to the FET gate to limit its tendency to oscillate. (Because of the parasitic inductance of the wire.)

For best results you would have exactly one connection between the grounds of the two systems at the FET source pin.
 
The current limits on the I/O pins is steady state so the pulsed current for driving a MOSFET is not a problem. You do want to put a resistor of 100 Ohms or so as close as possible to the FET gate to limit its tendency to oscillate. (Because of the parasitic inductance of the wire.)

For best results you would have exactly one connection between the grounds of the two systems at the FET source pin.

Thanks!

Do you have a suggestion for a less powerful logic level MOSFET (switching at most the 500mA 5V on the Vin)?
 
Just a follow up

Would a BS170 be a "good" logic level "low power" N_MOSFET?
I find the low capacity a bonus.

Are there better choices?
 
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