• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 65 subscribers
  • Views 1020 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.

Single cell Charger and Fuel Gauge - BQ24610 and BQ27541 - Is there a need for Protection IC

Alex Shpilsky
Intellectual 1000 points
Other Parts Discussed in Thread: BQ27541, BQ24610

 I’m looking at designing our battery pack with the BQ24610 and BQ27541.

The reference schematic for the BQ27541 calls out a protection IC MM3077 with some additional FETs.  Is this required?

I believe there is some overcharge/overdischarge etc. protection in the charger so this may be redundant.

Is there a newer fuel gauge with integrated protection?

  • 0
    TI__Mastermind 35165 points

    Hi Alex,

    Even though the charger you are using does have overcharge protection, the protection IC and FETs are needed to protect the battery.  Currently, we do not have any single cell gas gauges with the protection integrated.

    Regards,
    Anthony Fagnani

  • 0 in reply to Anthony F
    Intellectual 1000 points

    Hi Anthony,

    I seem to remember that BQ27550 had protection integrated, but I don't see BQ27550 as a released product. Do you know when it will get released?

    The customer still questions if they need to use MM3077 Protection IC. BQ24610 charger IC already has Battery Over-Voltage Protection and MM3077 also offers overcharge protection by monitoring  PACK+ voltage. It seems that this function is implemented in both ICs. What are we missing here?

    Another question they had: In lieu of the MM3077 and the FETs, how about just a PTC in series with the battery.

    Regards,

    Alex

  • 0 in reply to Alex Shpilsky
    TI__Expert 4050 points

    Alex, bq27550 will not be released.

  • 0 in reply to Alex Shpilsky
    TI__Mastermind 35165 points

    Hi Alex,

    Where in the system will the battery charger be located?  The typical system has the protection IC and FETs directly on the battery pack and the charger somewhere in the system.  If the charger is contained in the battery pack it will protect the battery from overcharge and overvoltage due to the charger only.  You will still want some over discharge protection.  When using the protection IC and FETs the battery becomes disconnected from the entire system if a fault occurs.  A PTC could work but its protection isn’t as effective compared to that of the IC.  It will react slower because it depends on a rise in temperature to activate.

    Can you give more on the application and do you need meet any standards with the battery pack?

    Anthony

  • 0 in reply to Anthony F
    Intellectual 1000 points

    Hi Anthony,

    The Charger and Fuel Gauge are contained in the battery pack, but I agree that protection IC offers a lot more protection than what the charger and/or PTC offers. I will forward your response to the customer.

    Thank you,

    Alex

     

  • 0 in reply to Alex Shpilsky
    Intellectual 1000 points

    BQ27541 data sheet specifies 1000ns data setup time for I2C interface. It seems kind of high. Is this a typo? Most of the other fuel gauge devices list 250ns as setup time.

     

    Thanks,

    Alex

  • 0 in reply to Anthony F
    Prodigy 20 points

    Hi Anthony,

    I have some suspect that the  protection circuit and FET are embedded in the battery pack (I know that Li-Ion cells are shipped only with such protection circuits for safety issues)... is this correct? 

    In this case do I still need to implement the protection circuit as well?