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I'm planning to use the LM2623 to boost a single AA for a 5V load that draws 400mA. This graph seems useful

enter image description here

The graph seems to suggest that at Vin=1.5V, there's no way 400mA could be drawn without a large voltage drop. At 200mA, Vout can be kept at 5V. I'm guessing that the load (if USB) will refuse to draw if the voltage is too low (<4.4V).

Is there a way to let it draw as much as it can from the input source? Could two DC/DC converters be used so that the first boosts the input from 1.5V to, e.g., 3V, and the second boosts the 3V to 5V. This way, at Vin=3V, the load could draw higher current (not for very long though).

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  • \$\begingroup\$ Can you use 2xAA? or a 9v or 12v? Have you considered that the AA will drop from 1.5v to approx 0.8 v over its discharge curve? \$\endgroup\$ – BenG Sep 6 '15 at 21:05
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There is a way, but it only works if your load is intermittent. You can use your source to charge up an electrolytic capacitor. When your load draws current, it'll draw from both the source and the capacitor at the same time, providing far more available current but only for short duration. Depending upon the current/duration you require, you may need to tweak the capacitor's charging rate or discharge rate, whether by capacitor selection and/or adding series resistance to the capacitor.

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