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BQ77PL900 communication blocked after error

Stefan Hittinger
Prodigy 40 points
Other Parts Discussed in Thread: BQ77PL900

While testing BQ77PL900 i produced errors that disturbed the system (voltage peaks, ground problems). Sometimes the communication via I2C is blocked and only power off solves this problem.

Is there any possibility to restart BQ without power off?

(These errors could also occur under normal handling conditions, so a battery pack would be unreachable...)

  • 0
    TI__Guru 54715 points

    Check to be sure the regulator voltages are still on.  If not, the device has shut down and it should wake up with application of the charger voltage (PACK pin > startup voltage).

    To "reset" the device, it would normally be shut down and re-started.  In host mode this could be done by turning off the FETs, setting the shutdown bit and pulling or allowing the pack and PACK pin voltage to go to zero.  Then apply a charger voltage. This won't work if there is no I2C communication.

    To do this in an engineering setup in standalone you would need to induce a UV condition without inducing an OV condition.  This might be accomplished by increasing the resistance to VC1 (or highest used VCx) and pulling it to VC2 (or VCx+1).  Simply shorting 2 inputs together may also induce a OV on the adjacent cell and prevent shutdown. Once the device has shutdown, wake it up with a charger voltage.

    If the device is really getting stuck, it is likely the transients are exceeding an abs max rating and the part could risk damage. It would seem best to find and suppress the transients thus keeping the device in its normal operating range rather than force a reset in-system.