LiPo charging with the MCP73833

I bought a couple of the nice LiPo chargers from Ladyada.

Its a nice little board with a strong JST connector and cable. The board has a cool feature in that you can adjust R4 to adjust the charge rate of the board. It comes stock with a 4.7KΩ SMT resistor in R4. That gives you a charge rate of 200mA. I soldered a 3.3KΩ resistor in the thru-holes above R4 so they are in parallel.

Since R = (R1*R2)/R1+R2 for resistors in parallel, that gives a total resistance of ~ 1.93KΩ and ups the charge rate to ~518mA or about USB max.

The datasheet says the IREG = 1000V/RPROGKΩ.

or 1000/1.93 ~= 518.

The chip on the charger is the MCP73833-AMI which has the factory VREG=4.20v.

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