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Device to be used in: solar-powered microcontroller with some peripherals attached.

Meant to operate whenever sufficient power is supplied (light is bright enough for a while). No battery, weather reasons.

Device is powered from a mp1584en buck voltage regulator, with large caps on both input (useful for solar, I think) and output (in case device needs more current for its nrf24l01 radio).

What I want to accomplish is a behavior where the buck gives no output when voltage on input side is too low (threshold to be determined later, expected ~9V of max 25V), but also to avoid it repeatedly turning on/off in low(ish) light, so turning back on shoud happen on a higher voltage (16V?).

Low-component-count solutions preferred, I'm not skilled enough not to mess up otherwise.

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As you have an enable pin on your regulator, the easiest way is to use something like a comparator to turn it on or off.

All you will have to do it set up a reference voltage and when your goes below the reference, your regulator sill switch off. Once it is above the reference again, it can come back on.

EDIT After the comment from @Transistor, I will add that if you use 2 comparators, you can give yourself an upper and lower threshold. This design is known as a Window Comparator. You could also consider using a schmitt trigger.

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    \$\begingroup\$ The OP seems to realise that hysteresis is required to prevent the voltage regulator turning on again when the voltage rises due to the unloading effect when the regulator is turned off. Your answer doesn't address this. \$\endgroup\$ – Transistor Nov 7 '17 at 8:40
  • \$\begingroup\$ Ahh, apologies, I clearly didn't read that correctly! I'll edit my answer \$\endgroup\$ – MCG Nov 7 '17 at 8:41
  • \$\begingroup\$ Sounds good, I forgot the regulator already had an enable pin, I bought ready to use boards with it. \$\endgroup\$ – kaay Nov 7 '17 at 10:55
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    \$\begingroup\$ Oh I see. Doing as I suggested should work, but you will have to hack the pre made board! \$\endgroup\$ – MCG Nov 7 '17 at 11:05
  • \$\begingroup\$ That's less of a problem for me than making one from scratch :) \$\endgroup\$ – kaay Nov 7 '17 at 19:05

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