• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 63 subscribers
  • Views 331 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.

BQ77915: Increase the discharge over-current limit

Ashish R
Prodigy 20 points
Part Number: BQ77915

I have a functioning BQ77915 cell balancing circuit. I just need to implement / increase the over-current discharge current limit for my existing design. With my existing circuit, I can implement the discharge over current upto 29A. I would eventually like to increase that to 50A or more.

My existing design components for BQ7791502: Rsense: 1mOhm ; ROCD:383kOhms for 180 ms programmable OCD delay

Other than changing Rsense, is there any other way to increase the discharge over current limit.?

  • 0
    TI__Guru* 81034 points

    Hi Ashish,

    The OCD threshold is fixed. It looks like the device number you are using has the highest available OCD voltage threshold. So the only other adjustment you can make is the sense resistor value. The highest possible OCD1 voltage value that can be set for the BQ77915 is 85 mV, but 70 mV is the highest option available on the currently released part numbers.

    How are you calculating the 29 A value? I calculate that you would need a 1.4 mOhm sense resistor for the OCD1 threshold to be set to 50 A. 

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Prodigy 20 points

    Hi Matt,

    Thanks for the reply. Yes, you are right, a 1.4mOhm Rsense should be able to handle OCD1 threshold of 50A (as per the datasheet). But when I tested with an actual 8S LiPo battery, it didn't work as expected. So, I used a Rsense = 1mOhm, which  gave me the 29A value for OCD1 threshold.

    So, other than Rsense, you do not recommend any other method to increase my OCD (discharge current) to 50A?

  • 0 in reply to Ashish R
    TI__Guru* 81034 points

    Hi Ashish,

    Other than changing the sense resistor value, there is no other way to increase the OCD threshold.

  • 0 in reply to Matt Sunna
    Prodigy 20 points

    Hi Matt,

    Thanks for the reply.