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[DPRG] Lithium Polymer battery charger Question

Subject: [DPRG] Lithium Polymer battery charger Question
From: Earl Bollinger earlwbollinger at comcast.net
Date: Mon Oct 13 07:38:01 CDT 2003

I would greatly appreciate it if someone could assist with determining
the current limiting resistor (Rset for the chip's Iset line) to use for
this.

I've built up a little (TI based BQ24012) PCB for a Lithium Polymer
charger in order to charge up some Small 135mah 3.7v cells for me to use
on my tiny robots. I also have some 155mah cells too.

Anyway, after going through the data sheets numerous times. I am still
stuck on the formula for determining the charge current resistor for the
ISET pin.
The data sheet seems to be missing something that I don't see to make
the formula work. I've worked the formulas with my assumptions as to the
value needed but I don't feel comfortable with the result. Considering
it took over 3 months to get these little battery cells I am reluctant
to "burn" test them. :)

Here is the data for the chips:
http://focus.ti.com/docs/prod/productfolder.jhtml?genericPartNumber=BQ24
012

http://focus.ti.com/lit/ds/symlink/bq24012.pdf

Thank you very much,
Earl






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