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BQ27541-V200: Questions about the Hibernation mode in BQ27541-V200

Part Number: BQ27541-V200

Hi,

Customer has some critical questions for the hibernation mode in BQ27451-V200. Could you help to check and give some comments?  

Thanks a lot.

---------------

I understand 

a: we need to setup [Hibernate] to 1 to exit from “Sleep” into "Wait_Hibernate". (We should follow TI instruction already and available to read out indicate from GUI control console, which means status set right through I2C).

b: then Average current()< Hibernate current or Vcell<Hibernate voltage, to exit from "Wait_Hibernate" into Hibernate mode. This is the point I need further brief. 

  • Question: What's the Average current sample period. Few seconds( 20 Seconds from above table) or minutes? I recall during former TI FAE discussion, he high light there's time delay to secure fully enter into Hibernation mode

 

c: Let's say If battery pack has enter "Wait_Hibernate" mode but fail to enter "Hibernate" due other reasons like I2C noise or Averagecurrent() take long time to below hibernate current? Which state will be back? Sleep Mode or WaitFullsleep mode? What Level of quiescent current should I expected 

 

 

d: we also understand BQ27451 will exit from Hibernate mode if there's communication activity on I2C and -V200 are very sensitive to I2C noise from TI FAE and below upgrade applied to -G1 version(slua641a).

  • Question: What's the software filter threshold value here to ignore the I2C noise, few seconds or minutes?
  • Hi Oliver
    a-yes hibernate flag has to be set
    b.Average current is the value reported every 1s.
    c. Gauge will be in which ever one whose criteria is met, either waitfull sleep, full sleep or wait hibernate.
    d. I believe the device i2c engine checks for an actual start condition

    thanks
    Onyx
  • Hi Onyx

    Thanks for answering. Actually Oliver help me to post the answer into your Forum. Both my customer and myself has contact with TI FAE from US and Asia few months ago, just recently some new topics on hibernation comes again and team seeking the help from myside again.

    Back to my questions.

    Question b: from some verify by my battery pack supplier has taken, they might need up to 5 minutes before pack really go to Hibernation mode and we know it's difficult to verify if it really going to Hibernation or not under Mass production setup. I'm wondering if sampling current just need 1s, we shouldn't need such long time to enter. Does 27541 FW also do averagecurrent weighting  by few duration(for example, few second or few cycle, assume BQ might have soft filtering to ignore false trigger).  

    Question c: Can you brief more on this exit logic(assume slua641-Figure 3), I can't attach picture here.

    Question d: From former communication with TI FAE, we understand -V200 is most sensitive(even by touch on the wire might exit from Hibernation), thus -G1 and 27542 are promote to represent -V200. As said, we want to avoid design change, so we need better understanding how circuit is expected to behavior on certain failure trigger then think how we can avoid from handling. Will -V200 been trigger even by a pulse on SCL/SDA. what's the software filter under -G1 version to make enhancement as "Device will only wake from HIBERNATE if I2C traffic is addressed to the fuel gauge", to me it's just a software filter to make sure that's real traffic.

    Thank you for your help

  • the gauge needs to take an OCV measurement before it can enter hibernate. That is the reason for the delay.

    -pls take a snippet and attach the image in question. there is an attach oin button.

    -Changes were made in the firmware that prevents the issue on the new firmware. It is not just a software filter.

    thanks
    Onyx