U2 = U/Rges * R2
A0 will be (VCC-Vf)*R2/(R1+R2)Plug in the numbers.Should not affect the PWM waveform unless R1+R2 are really low values. If R1+R2 = 10K total for instance, and VCC = 15V, then current draw from Vcc will be small, just 1.5mA, which will be a good amount to drive the A0 input.
Why the A0 pin. Are you expecting a 'voltage' into the pin from that PWM signal?I would expect you use a digital pin to measure the PWM on/off times.Leo..