GEOFEX Charge Pump current draw - how much

[bdevlin]

Anyone have a notion of how much current draw there is with a MAX1044 charge pump.  I'm speaking specifically of the 17 volts from one battery version.

[Paul Perry (Frostwave)]

The draw from the input battery, depends on how much current is being taken by the output.
As a very rough guess, I would say the input current would be twice the output current (because that is the theoretical no loss minimum) times say 1.3 or so.

[R.G.]

Really good guess, Paul. First Law plus Second Law. Actually, the efficiency is a little better than 70%, but that's a conservative number to use.

@bdevlin: notice that the output current needs to be less than 10ma for the 1044 to supply it in good order. More than that,  you need a couple of 1044s in parallel or some other style converter. Run your indicator LED directly from the battery, not from the 17V out of the 1044.