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waking from sleep after charging

Other Parts Discussed in Thread: TPS62200, BQ24032A


The problem is still a little vague but here is what we know.

We are having problems with our product not waking from sleep after charging - perhaps 1% of the units out in the field.  The problem is intermittent and not repeatable on demand. So far it seems to be related to AC charging, not USB charging (although few customers seem to use the USB charging). At this point we don't know whether the problem occurs with the charger plugged in or not. When the charger is plugged in, the unit is powered by the charging source and not the battery. The unit goes to sleep after 5 minutes of no activity from the user and draws about 300 - 400 uA in sleep. When the unit doesn't wake, it appears to be dead but with a charged battery as if there might be some interruption of power to the processor - enough to stop the processor but not long enough to cause a reset.

We've thought about the possibility of power spikes from the power source causing an interruption of power to the processor, but don't know how likely this is. The processor is powered from the output of a TPS62200 which is powered from the VSYS output of the bq24032A. Another thought was an issue with the switching of the power to VSYS from the charging source to the battery when the charging source is removed.

Have you seen anything similar? If not any idea what we should be looking at to try and see what's going on?


  • I have not heard of this type of issue.  The bq2403x charger is designed to switch to the battery power whenever input power is removed and typically does it in ~10us, so if you have more than 10us of hold up time then there should be not drop out in power.  The data sheet requires at least 50us of hold up time.  Also it does not sound line the battery voltage is down at the minimum process voltage so my guess is that it the bq2403x is not involved, but if you capture some waveforms we can make sure.  I am less familiar with the TPS part and will let someone else jump in.

    It would be nice to have a block diagram of the system configurationa and schematics of the problematic circuit and some photo shots or we will just be guessing.