Series resistors in a LPF followed by voltage divider

[mark2]

Immediately after posting this I realized it was probably terribly flawed.

If I want a low pass filter to smooth out a 5V PWM signal, then a voltage divider to bring it down to 3v3.... does the following make sense?

10k + 100n chosen first (or whatever the best values turn out to be) for the filter... then using 10k as a given, calculate 20k as the resistor for R7 in order to bring the signal down to 3v3. Is this correct?



-----old flawed idea below---------------

I want a low pass filter to smooth out a 5V PWM signal, then a voltage divider to bring it down to 3v3.  Do I

Are these two functionally identical, and if so are there any reasons to keep two separate resistors?



Thanks! Happy new year.

[Rob Strand]

Looks like you got it right.

R7 (20k) determines the  "DC gain".

The filter cut-off is affected by R7.  You need to use R = "R5 in parallel with R7" to determined the filter cut-off.

[mark2]

The filter cut-off is affected by R7.  You need to use R = "R5 in parallel with R7" to determined the filter cut-off.

I didn't think of that, thank you.
So it sounds like lowering the cap to 150n should do the trick.

I may need to experiment with the filter values or do more research anyway since I blindly copied the 10k 100n from somebody in another forum.