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Basic Electronics » Can someone help me with LDOs?

August 21, 2013
by Pew446
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I have a circuit where I want to convert 6 volts from 4xAA batteries to 5 volts to run my ATMEGA328-P. I also want to drop that 5 volts to 3.3 volts. I found two parts on Tayda which seem to do this:

5 Volt LDO

3 Volt LDO

What I can't seem to find anywhere is any tutorials on how to use the things. They both seem to have two outputs, which is confusing to me. Would a circuit like this be correct?

LDO (Same for 3.3V, except with 5V input and 3.3V LDO)

Can anyone help me get in the right direction? Is this the best approach?

August 21, 2013
by Noter
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There is only one output pin. It is also internally attached to the tab but still only one output. Just remember not to ground the tab and all will be well. Yes your circuit will work but you probably don't need the cap on the input since your source is pure DC from a battery. The output cap could also be reduced to 1uf ceramic or less depending on the circuit you are driving.

August 21, 2013
by Pew446
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Thanks again Noter! :)

August 21, 2013
by Noter
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Also instead of connecting one LDO to the battery for 5v and another to 5v for 3.3v, connect both inputs to the battery and minimize the load on the 5v ldo.

August 21, 2013
by BobaMosfet
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There's a better, and less expensive way to do this. Use a diode instead to drop 1V (so 6V to 5V), which will give you polarity protection, and then you only need the 1117 for 5V to 3.3.

BM

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