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Hans, Also take into consideration that this issue is likely to be amplified by the rapid decrease of the capacitance of the X5R/X7R caps (in case you used them)??C102, C104, C105, C502, C507 under the influence of voltage increase (0->5V->12V). Q=C*U? where Q is constant, but C decreases (e.g 10%) under the influence of increasing U -> making U even higher (e.g. 10 times higher). Indeed, with L101 about 1.5R or so supply?DC-resistance, the 1ms software control loop is way too slow and should be in the order of 4ns response time to correct the voltage in C107, difficult to achieve in a ADC polling fashion so this is probably a NO GO as it would have a serious CPU cost. A simple workaround could be to DELAY the use of switching regulators after powering up. This allows the USB PD device to do the voltage jumps just while only the LDO is active, and limits the sensitivity in all these control loops that are anyway too slow to resolve this issue. As soon as there is a voltage drop (due to a bad cable) you could redo the complete power-up procedure to also be immune in that circumstance. My view on this is that all effort you put in making the control loops faster will eventually still insufficient to deal with this USB PD voltage steps. 73, Guido On Sun, Sep 3, 2023 at 3:20?PM Hans Summers <hans.summers@...> wrote:
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