LiPo Charger Booster Circuit Problem

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I used SparkFun’s PowerCell (https://www.sparkfun.com/products/11231) in a prototype product and then integrated the circuit onto our main PCB board. It has stopped working after about 4 months of use and I am having a very hard time trying to debug the issue. I just can’t find anything wrong. I think there must be something wrong in my component selection or design - because I had weird issues when I first tried the circuit. I quickly had to replace the chip and it seemed to work fine for several months…

-The battery is fine

-The charger part of the circuit works fine

-I have made very few changes to the original circuit

-There is nothing on the boost chip’s output

-Voltages on all control inputs look fine

-I am reading 4.2V on my USB 5V line when the circuit is activated… This seems strange

-I have never witnessed the main circuit draw over 400ma and I have tested in peak conditions.

Info on the circuit here: https://docs.google.com/document/d/1T1H … momOE/edit

Eagle files: https://drive.google.com/file/d/0ByaeK3 … sp=sharing

https://drive.google.com/file/d/0ByaeK3 … sp=sharing

(first real Eagle project ever…)

I would be so appreciative of any advice - this is driving me crazy.

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Not looking at the design, I will say that there is more variables than just the design and voltage. Read the datasheet for info on soldering temperatures and/or maximum temps. This can affect the life of a chip.

Did you test the how much current is being consumed while at the 4.2V? For the voltage to fall that low, it sounds like there is a lot of current consumption due to chip failure.

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Soldering temperatures are not something I had considered - will look into this - thanks. We did heat the whole chip with a laser.

As for the current - I haven’t measured it since seeing the 4.2 V. I assumed the current was still < 500ma since the fuse hadn’t blown though.

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I’m also interested in resolving this question, since I plan to do the exact same thing with a board I’m designing, and It’ll be one of my first EAGLE projects. Scottas - have you made any progress on this issue?