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BQ24022 falls into an undefined state - starts heating rapidly

Other Parts Discussed in Thread: BQ24022

Hi everyone,

in our devices we're using BQ24022 as a battery charging IC, to charge the LiPo battery.

It is a consumer device and under some circumstances while charging, the BQ24022 falls into an undefined state and starts heating up rapidly.  At that point even toggling the CE (charge enable) pin does not get the BQ24022 back to the operational mode. 

STAT 1 and STAT 2 pins are connected to our host MCU, with internal pullups on those two signal lines.
When BQ24022 is working normally and STAT 1 and/or STAT 2 pins are active, we measure 0.00 Volts on those two signal lines. (when inactive, the pullups bring these two signal lines to 3.3 Volts)
But when BQ24022 falls into the undefined mode, we measure 0.10 Volts on STAT 1 and STAT 2 lines.

BQ24022 falls into the "undefined" mode only after we mount the device electronics into final enclosure, where there is a metal plate mounted close to the electronics. This metal plate is floating (not grounded) and seems to be acting as an antenna, that picks up and spreads ambient noise/interference. (If the metal plate is grounded, or not mounted at all, we have no issues with BQ24022 falling into undefined mode).

It seems like that interference puts the BQ24022 into undefined mode and the only way we are able to bring the BQ24022 back to normal operation mode is to remove the charging cable.
We are using MicroUSB cables for charging and BQ24022 is set to 500mA charging.

Is this a known issue related to BQ24022 ?
What is the reason for BQ24022 to fall into such undefined mode and why is the CE pin toggling not functional ?
Is this caused by noise on the supply lines coming into the BQ24022 (we are using USB supply only input), or is this caused by noise generated on the battery lines, that are as an output from BQ24022 ?

It seems like BQ24022 is shorting the input to GND in the undefined state. Is that right ?

We are in a time critical position right now, so any help is greatly appreciated.

Best regards,

Rok Zalar