The microcontroller uses a timer to generate the PWM signal. The timer counts up from 0 to a maximum value. When it reaches the maximum, it resets to 0 and starts counting again. The Duty cycle is determined by the value at which the timer output switches from low to high. For 8-bit resolution (UNO): The timer counts from 0 to 255. To achieve the maximum PWM frequency, the timer should overflow as quickly as possible. So, the maximum PWM frequency is the clock frequency divided by the maximum count: 16 MHz / 256 = 62.5 kHz. For 16-bit resolution (ESP32): The timer counts from 0 to 65,535. Using the same logic, the maximum PWM frequency is 16 MHz / 65,536 = 244 Hz. In essence, higher resolution requires the timer to count to a larger number before overflowing, which takes more time. This directly limits the maximum possible PWM frequency.

... the digital pins ON and OFF at a very high frequency creating a dummy analog signal. And there are 6 digital pins on UNO that supports this behavior- with a "~" symbol next to them (like 3, 5, 6, 9, 10, 11) When you use analogWrite(pin, value), you're controlling the Duty cycle of the PWM signal A value of 0 means the pin is off all the time. A value of 255 means the pin is on all the time. Values in between control how long the pin stays on during each cycle, effectively simulating an analog voltage between 0 and 5V. So analogWrite function has nothing ...