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I am working on a small, solar-powered application that makes use of RF and a few higher-power sensors. Those will only be on for a fraction of the time, but might consume 1A-2A at 3.3V.

The remainder of the time, a low-power micro-controller will be doing house-keeping, monitoring the charge of a super-capacitor, and enabling the high-power load when enough charge is available (and some other criteria are met).

I have been working with the LTC3108 on this, but this has a current limit of 300 mA, which now proves to be a problem.

Do you have recommendations for other parts, or a combination of parts, that would allow me to tackle this?


My requirements:

  • controllable 3.3V output 1A-2A (only briefly used)
  • input from solar cell (e.g. 1.5V, 26 mA peak - but could be changed)
  • always-on 2.2V or 3.3V output for low-power μC
  • a super-capacitor that stores the harvested energy (e.g. 2F 5V - but could be changed)
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  • \$\begingroup\$ Use conservation of charge and energy to see what must go in and out and ESR for load regulation error. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 21 '18 at 15:33
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Just imaging your high power circuitry as one "device" and your low power stuff as another.

Now, branch the power from the super capacitor to the 2 "devices". The low power branch can be permanently connected, but for the high power branch use a p-channel mosfet to switch the power on and off. You can use an NPN transistor to pull the mosfet gate down.

Now the only other thing you'll have to be careful of, is to not parasitically power the high power systems through the IO. Basically you'll have to make sure that all the data lines are kept low. If any of them are high, power will flow into the high power side through the protection diodes.

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