[Runtimemicro] has the answer, at least if you are writing PWM code for the Arduino. Their free application lets you set a few parameters, visually see the results, and then generates code for you.

In this tutorial, T.K. Hareendran shows us how to set up an interleaved PWM output on an Arduino Uno. He then uses different techniques to validate that the desired result is achieve.

Lastly on that connector is the spindle output and, just like the 36V fan output, the connections are: +ve directly connected to the 36V power input and -ve modulated to 0V from the cnc domain by ...

The machine uses a ‘grbl’ controller, which has an Arduino-based circuit that includes multiple outputs, including a powerful 24V pwm signal that is generally used to drive a 60-80W spindle motor.