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BQ76940: wake up issue in BQ76940 SHIP mode

Peter Chen(ICP_FAE)
Intellectual 2480 points
Part Number: BQ76940

have a function issue, BQ76940 from SHIP mode to wake up, protection IC alert pin keep high level & couldn't cleared, internal fault (SYS_STAT 0x20), please check as below. If there want more detial, please let me know, 

 Any tips, sequence require is necessary form protection IC normal to SHIP mode & SHIP to normal mode? 

How to clear or reset this err by FW? 

Meter check while ALERT keep high.   



Oscilloscope SCK SCL signal check, (MCU request protect IC clear err.) 

  • 0
    TI__Guru 54715 points
    Hi Peter,
    Status register 0x20 is the DEVICE_XREADY fault. This indicates the part has trouble communicating between the cell groups. Common causes of this are:
    No power to the upper groups, but your voltages look OK.
    Shorted CAP2 or CAP3. After boot these should come up to 3.3V across the cap, same with CAP1. (Each will have a different tolerance).
    Residual voltage on TS2 or TS3, this can prevent the upper group from waking up on the boot command. Be sure to operate with the thermisors attached or a similar pull down resistor.
    Pulling TS2 or TS3 below the local reference. Be sure the thermistors pull to the appropriate local reference (VC5X, VC10X) and not to VSS. Current out of the TSx pins can prevent boot and cause XREADY.
    An incomplete transition to ship mode. It takes time to complete, boot before complete could cause XREADY. Be sure the CAPn voltages have gone to 0 before boot (troubleshooting step).
    Noise on TS2 or TS3 before boot causing the middle or upper group to wake up. Again use the pull down and check the voltage before boot.
    If XREADY occurs but the part is on you can clear the status as you are doing and continue operation. It appears you have a CRC part, be sure your MCU is sending the proper CRC value or the clear will be rejected.
    Look at the cell voltages read from the device. If all report 0 the problem may be with the middle cell group, check CAP2 and TS2. If the bottom group (cells 1-5) reports cell voltages but the upper groups do not, check CAP3 and TS3.