Reported by daveshah, Jul 23, 2020

PWM frequency needs to be increased from 83Hz, as the recommended 
range for the LM3699 [1] is between 2kHz and 100kHz. As there is an 
internal low-pass filter, the intention is that this actually 
becomes an "analog" control rather than PWM giving an 
essentially flicker free output above 4kHz or so (see figure 15).

Should be an easy change, just posting this to keep track of things.

[1] https://www.ti.com/lit/ds/symlink/lm3699.pdf