So I have this relatively difficult system to power, it needs three voltages to operate, 5V before anything else, then after it has been stable long enough, 3.3V and 1.2V can be applied.
But the voltage between 3.3V and 1.2V rails can never be larger than 2.5V or -1V, meaning that if 3.3V rail is still 0V, the 1.2V rail must be limited to 1.0V or smoke happens. Or if 1.2V rail is still 0V, applying more than 2.5V to the 3V3 rail means smoke again.
So okay there are tracking regulators, so I can make the 1V2 track the 3V3, and for the tracking to work fast enough I can use a 3V3 regulator with slow start so 3V3 ramps slowly enough. And I can use the microcontroller to control 3V3 regulator so 5V has enough time to stabilise.
But how to make sure on sudden loss of power situations the thing shuts down gracefully? I don't want to have the microcontroller to be responsible of monitoring the voltage or shutting down the regulator.
Any pro tips like voltage monitoring chips or regulators that have also slow shutdown capability?
I guess I could make the 3V3 track some input power supply perhaps? Some Schottky diodes so that 3V3 rail pulls down the 1V2 rail as well?