Using Funky’s boost regulator get steady 3.33V from higher voltage

I would typically think of a boost regulator in the case when I’d like to step-up voltage, and such were my intentions when I introduced the LTC3525 boost regulator chip on the Funky sensor. The idea was to be able to power the Funky from a single AA/AAA batery, and the LTC3525 would simply provide steady 3.33V until the battery drains down to 0.5V. Quite neat way to squeeze all the juice out of a battery, proclaimed ‘dead’ by other electronics. I was browsing today the specs for the AA power board by Jeelabs (I own one, but never carefully read the description), and it is powered by the same chip. I was surprised to read

The board uses an ultra low-power LTC3525 boost regulator chip which draws only 7.. 30 µA of current in idle mode (depends on input voltage). The input can be anything from 1.0 to 5.5V, so this can also be used with 2x or 3x AA battery packs (even 4, if NiMh), and it will continue to work when hooked up to a 5V power supply. The regulator will work down to less than 0.5V and can squeeze the very last bit of energy from the battery.

 

Wow, this is something I have completely missed..The LTC3525 will not only step-up voltage, but when it is higherthan the desired 3.33V it will also reduce it. Neat! That means that if I hook 3xAAA batteries to a step-up version of the Funky, it will run for ages..Could come in handy.

So will I drop the voltage regulator (MCP1703) that I also have on the Funky? The answer is not quite. The LTC3525 is quite expensive, and in can only handle up to 5.5V input. The MCP1703 on the other hand is much cheaper and can do higher voltages.. so I’m keeping both, one can decide which option to use based on the use case.

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One thought on “Using Funky’s boost regulator get steady 3.33V from higher voltage

  1. The LTC3525 will not only step-up voltage, but when it is higherthan the desired 3.33V it will also reduce it.

    Is this true? As far as I understand the datasheet, it’s just a step-up converter until V_in reaches 3.3V and after that, V_out will rise with V_in. Which means that for V_in > 3.3V, the circuit is somewhat bypassed.

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