I am trying to switch a IRL520N logic-level MOSFET using a 0-5V PWM signal from my microcontroller (PyCom FiPy).
I tested just the MOSFET with a 10 Ohm series gate resistor and my load is a 9-15V brushless DC pump (TD-3LS from this manufacturer). I had my load rail at +12V and a power supply driving the gate at around 2.3V-4V. The pump ran just fine.
Then I hooked it up to a function generator to test the PWM signal at the gate. I tested a variety of amplitudes (0-5V, 0-10V), frequencies (500mHz to 5kHz), and duty cycles (0-100%). None of them turned on the MOSFET and ran the pump.
I've attached a schematic of the final pump drive circuit that this MOSFET will be going into and the original designer said that he got it to work with a PWM signal of 5V, 2.4kHz, and 0-100%, so I'm not sure why I can't even get the MOSFET to work on it's own (note: I've also tested this circuit with a variety of PWM signals and steady drive voltages, and could not get it to switch on the pump).
EDIT: I was able to get the pump running off the IRL520N MOSFET. It needs to run for a few seconds at 100% duty cycle first before switching to a pulse (duty cycle was 50-75% at a frequency of 500 Hz from the Arduino). However, still not able to get it running with the driver circuit below, so open to any suggestions about what could be wrong with that. I thought maybe I wasn't giving enough time for the capacitor to charge up so I ran the pump at 100% duty for 20s before switching to the PWM, but still nothing.