[sdiy] Driving SSI2144 freq control with PWM from a microcontroller

[Neil Johnson]

Hi all,

Genuinely curious question: since you're driving a low-pass filter
anyway, why not dispense with filtering the PWM and, assuming the PWM
clock is way above audio, just drive the frequency control pin
directly?  You'll be driving the transistor ladder directly from PWM
so it would behave more as a switched-capacitor filter rather than in
linear mode, but it might work.
For the SSI2144 that would be, say, +/- 90mV pulse waveform.

Neil