• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 113 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ76920: UV_Trip = 0?

Jeffrey Wright
Expert 2875 points
Part Number: BQ76920
Other Parts Discussed in Thread: BQSTUDIO, BQ78350-R1, BQ78350

Hello;

My client is reporting that the CUV protection isn't working. The 78350's CUV threshold is programmed to 2.3V. However, reading the AFE_Config registers shows that its UV_Trip register is 0 ?

BqStudio confirms CUV is correct...so why does the 920's register read 0? What could I have done to cause this???

ThanksUV_Trip.docx

  • 0
    Expert 2875 points

    Forgot to ask: I note that the 920 datasheet says that these thresholds are computed using the factory calibrated gain and offset. Can you confirm that the 78350 uses the formula as listed in the 920 datasheet which describes how to compute the actual UV_Trip using the gain and offset?

    Thanks

  • 0 in reply to Jeffrey Wright
    TI__Guru* 81034 points

    Hi Jeff,

    Since you are using the BQ78350-R1, the CUV of the AFE is programmed in the AFE SUV Threshold. It is automatically calculated using gain and offset. You may want to try changing this threshold to verify that the AFE_Config register changes as well. Another important thing is you need to enable the SUV PF in the BQ78350.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Expert 2875 points

    Ok, thanks Matt; That explains the 0.

    But my when client drops the cell volts to 2.1V, they're telling me that the discharge remains enabled? And mine only opens when Vcell is < 2.85V...when BqStudio says the CUV is 2.300V?  My client says that the AFE cell volt readings appear very accurate, so why would the CUV threshold be off by ~20mV?

    Thanks!, 

  • 0 in reply to Jeffrey Wright
    TI__Guru* 81034 points

    Jeff, 

    I'm not sure - I would need to see a log to see why the discharge FET opens. The cell measurement voltage is less accurate at lower voltages according to the datasheet, so that might be what they are seeing. There is also a programmed delay, so they should consider this if they are ramping.

    Remember that CUV and SUV are different. UV_Trip is associated with SUV (CUV for the AFE).

    Matt