• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 543 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.

BQ76952: CUV protection is not working!

Duc Nguyen
Prodigy 21 points
Part Number: BQ76952

Hi expert.

I have question about CUV protection. My value setting in register: 

Settings:Protection:Enabled Protections A is 0xFC (enable all protection)

Settings:Protection:CHG FET Protections A  is 0x98

Settings:Protection:DSG FET Protections A is 0xE4

 Protections:CUV:Threshold is 50 (protect when cell voltage under 2530 mV)

Protections:CUV:Threshold is  74. 

When I connect  BQ76952 in BMS with battery have under voltage, voltage each cell in range 600mV-700mV. I read Fet Status Register  have no Alert (value Fet Status Register is 0x48 and value ALRT_PIN is 0) and Safety Alert A Register is 0,  Safety Status A Register is 0. I don't know why BQ76952 don't protect CUV. 

Can you give me some guide to set CUV protection?

Thanks and Regards

Duc Nguyen

  • 0
    TI__Guru 54715 points

    Hi Duc,

    I don't understand why you don't see CUV.  When I write Settings:Protection:Enabled Protections A is 0xFC with a default and about 600 mV on all cells I see the CUV appear in Safety Status A.  The other settings above seem to be default if your note of Protections:CUV:Threshold is  74 is actually Protections:CUV:Delay is  74

    Check that the register display is really updating. Also be sure there is not a RESET sent or voltage dip which would reset the part.  RESET will clear the Settings:Protection:Enabled Protections A back to 0x88 and there is no CUV

    T

  • 0 in reply to WM5295
    Prodigy 21 points

    Thanks for your response, something wrong with my note, the value of register Protections:CUV:Delay is 74 .

    I have checked register Settings:Protection:Enabled Protections A and  this value is 0xFC and  the value of  Safety Status A is 0. But I read Battery Status Register is 0x18C,  the value of POR bit in the Battery Status Register is 1. Maybe some event makes it is always set. I will check it.

  • +1 in reply to Duc Nguyen
    TI__Guru 54715 points

    Hi Duc,

    Battery Status Register 0x18C is common after reset.  Again be sure you are not getting an unexpected reset and losing your settings, but it seems you have confirmed this.  When I set the Enabled Protections A to 0xFC i see a value of 0x0984.

    Also check Vcell mode value.  Default is 0x0000 which selects all cells, this is somewhat confusing since 0xFFFF would also be all cells.  If you have a non zero value it will not detect UV on a cell with 0.

  • 0 in reply to WM5295
    Prodigy 21 points

    Hi expert,

    Finally, I have found the reason make the device does not protect CUV. Something wrong with my configure. When I set the device into config update mode, it actually does not enter config update mode, and my setting value is written in data RAM but not operation. It could result in unexpected operations (as TRM said). I have modified it and the device works very well. I can see the CUV appear in Safety Status A.

    Thank you so much for all your support!