How to transfer the duty of a PWM signal to a accurate voltage

[bluesmaster]

the frequency of the input pwm signal can vary from 5K to 10K.Need a circuit to transfer the duty of the PWM to a voltage or current with 8bit resolution whatever the frequency is . Anybody can help or give some ideas.

 

[jpanhalt]

Would a simple low-pass filter like this work:

That circuit was just chopped out of a larger design, but I show it just to give you the idea.

John

 

[bluesmaster]

Thanks a lot.But it is impossible to build the 10uF on chip.

 

[jpanhalt]

It was just an approach I used to convert duty cycle at a fixed frequency to a servo control. The frequency was much lower, so my capacitor was larger. Values can be adjusted for different frequencies. I suspect it would not work too well, if the frequency and duty cycle are changing together. In that case, a purely digital approach or a clocked integrator might work.

John