A power sequencing scheme was designed to ensure deterministic behavior on power-up. The regulators are sequenced as follows:
It is important to validate the power sequencing experimentally, to estimate the time needed for the board to be in a working state. The scoped signals are as follows:
It can be seen that the power sequencing does not exactly follow the initial estimation. The most notable discrepancy is in the +A3V3 power rail (low-noise 3V3 rail), which has some sort of soft-start feature. This is an important feature to note, as the moteus firmware uses this rail as a reference for ADC measurements at boot-up, to determine board family and version.
The modified power sequencing graph is as follows:
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