Lex
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If I apply zero input signal, and if I sweep over time, at the digital output higher noise is seen as function of time. If I plot the variance over time, it really gives me the 1/f characteristic.
Your remark about the rectifying capability of the bandgap is an interesting one! The only coupling can occur via substrate/ground or supply, as other disturbing signals are >50 um away. Most of the wires are shielded with ground. So if I understand you correctly, this ground bouncing (basically a 5mv pulse of a few us every 100us), could show up as as low frequency noise at the output of the BG? Interesting! I will check this effect with a simulation on the extracted version.
I will have a range of chopping frequencies available, so I can always select another frequency externally if some noise source appears to be on the chopping frequency.
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