This is why you use PDM, not PWM. The pulses are at much higher frequency and easier to filter to the correct DC level with less noise.
From: Synth-diy on behalf of brianw
Sent: 20 March 2026 08:22
To: synth-diy@synth-diy.org
Subject: Re: [sdiy] Linear response VCOs?
Sent: 20 March 2026 08:22
To: synth-diy@synth-diy.org
Subject: Re: [sdiy] Linear response VCOs?
The challenge with PWM is that changing a rail-to-rail square wave into a steady DC value requires a lot of filtering. That filter must remove the sharp rise and fall of the raw PWM output, and thus the DC output value cannot sharply
rise or fall either. The problem gets worse if a single channel needs to feed multiple unrelated CV values through a mux+S&H. The slew rate is horrible.
Brian
Brian