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Power Regulator

A project log for A Beacon Battery System

A low cost smart battery for Bluetooth Beacons

gb-clark-iiGB Clark II 04/10/2018 at 11:010 Comments

The Power Regulator:

The  MAX 882:  This is a 3.3 V, 220 mA  LDO that was designed to be run off of a battery.  It uses a P-Channel FET to consume a max of 15 uA during operations, has a  typical drop out voltage of 220 uV and has a variable output among other features.  In this case I set the output to 210 mA, and told it to go into standby when the batteries output hits 3.14 V, no reason to kill the battery if I forgot about ti for a little while.

Unlike a lot of other regulators, it does NOT care about the ESR of it's input/output capacitors, as long as the minimum values are met.  This meant that I could use electrolytic caps as long as I was careful to de-rate them for temperature. Most likely I will end up adding a  ceramic or tantalum in parallel just to be one the safe side.

Yes, I know switchers are more efficient, but you've got to remember that this things entire purpose is to power a Blue Tooth module and I want a power supply that is as clean as I can get.  Short of heroic efforts, a switching power supply will always generate more noise, and I'm lazy.

Next up, laying out the system.

TODO document the two voltage points (output and standby) and my reasons for doing so.

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