--- In Ilya Goldberg <> wrote:
Do you attempt to limit the inrush current, or is momentary (but HUGE)
load not a problem for your powersupply? My switchers would refuse to
power up with a setup like that :-(
> I solved the graceful-shutdown problem a different way.
> I used a TS7260 because it has an on-board power supply that allows a
> wide input voltage range. Its on-board ADC is conveniently connected
> to Vin with a voltage divider, which lets me monitor Vin in software.
> I then put 3x 2.5F/5.4V super-caps (in series) across Vin, which gave
> me a UPS from 12 V (nominal, lead-acid battery+charging system) down
> to 4.5 V or so when the power-supply would give out. You need low-
> ESR supercaps for this to handle the board's entire load.
> This gave me several seconds of running time depending on what was
> plugged into the board (just a USB flash drive in my case).
> This cost around $15. I used EMHSR-0002C5?005R4 from Nesscap, but I
> see digikey doesn't sell them anymore, so I'll have to find something
> equivalent next time.
>
> I wrote a polling-program (userland, not kernel) to poll the ADC
> every 100mS, and do a shutdown if Vin dipped below a configured
> voltage. Since there was no convenient way to halt the CPU and bring
> it back up if the voltage never got low enough to actually shut it
> down, I just shutdown my application (separate program), dismounted
> all the filesystems and left the polling program running. This let
> me re-mount everything from within this program (and restart my
> application) if the voltage climbed back up to a preset "turn-on" level.
> The TSBAT3 scared me away because it just seemed way too complicated
> (and expensive).
> Supercaps don't last forever either, but they last a good long time
> if they don't get too hot.
> No charging programs or circuits, just dump the upstream power supply
> straight into the supercaps (which is a very big load if they're
> fully discharged).
> Works great.
>
> -Ilya
>
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