Noise. Most - if not all - of these chips have analog to digital convertors because most of the applications involve monitoring some sort of signal. There's goi

Noise. Most - if not all - of these chips have analog to digital convertors because most of the applications involve monitoring some sort of signal. There's going to at least a bit or two of noise in the signal (or if not otherwise used, a floating input.) That's where I'd start if I was looking for entropy.