I have an application with a Li-Ion Poly battery soldered to my board. I put BQ29700 on my circuit board to provide protection against over current (act as a resettable fuse) and undervoltage damage to the battery.
So far I've been powering on a bench supply with 3.4V. The BQ29700 appears wrongly not to assert DOUT to turn on the FET. It only happens about half the time. Am I doing something wrong with my circuit:
- In none of my tests I've been drawing any high current.
- Shorting across R10 with tweezers does not get it out of this mode.
Shorting across the transistor Q2 does get it out of this mode. It's as if I must get the current flowing to jump start it.
- Pulling DOUT high sometimes gets it out of the mode, as if once current starts flowing and developing voltage across Pin 6 and Pin 4, it turns on the FET. It could also be that pulling up DOUT has some other effect, such as briefly tripping current limit on my supply, which I've been setting in the 150mA range.
- Replacing the part does not work. I've seen this behavior on three boards. Changing out the BQ29700 didn't help. I can't detect any shorts, and I believe there is sufficient solder on all pads.
Can someone suggest some things to look for?