• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 230 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.

BQ24620: Charge Current Settings Explained

Alex K16
Intellectual 300 points
Part Number: BQ24620

The BQ24620 data sheet makes comments about the usage of the SR resistor (section 8.3.2) and how it influences the maximum charge current but I got confused by comments about using "larger" sense resistors.

Our application calls for 1.25A maximum charge current. I am not sure if I need to alter the resistor network connect to the ISET pin or just set the SR resistor value to 0.08 Ohms.

Thanks,

Alex

  • 0
    TI__Mastermind 24075 points

    Hi Alex,

     The max voltage you can source on ISET is 2V, and for a 10mohm sense resistor,  this will result in a max charge current of 10A. To increase the charging current beyond this you would need to change the sense resistor, so that is why the description of changing max current is related to the sense resistor.

    For your application that has a max 1.25A charge current, you can use the 10mohm sense resistor and just control the voltage on ISET that corresponds to 1.25A

  • 0 in reply to Kedar Manishankar
    Intellectual 300 points

    Hi Kedar,

    In such case please explain how to do that using R7 and R8 resistors. My calculations show that I need to set ISET to 0.25V to get 1.25A current from 0.1Ohm sense resistor.

    By default they have values of 100K and 22K giving the ISET the value of 0.6V (between 3.3V and 0V), which makes no sense to me. I have struggling to understand where does the default 2V comes from here.

    Thanks,

    Alex

  • 0 in reply to Alex K16
    TI__Mastermind 24075 points

    Hi Alex,

    A simple resistor divider from VREF to GND centered at ISET, with resistors sized according to what voltage you need will suffice.

    If you are looking at the schematic of the user guide the resistors are sized to give a default 3A charging current.

    Page 6 of the datasheet in the Electrical Characteristics table (under current regulation fast charge) shows the max range of VISET.

    I have not referred to 2V as default, but as the max you can source on ISET. Please refer to this post and my above post for answers to your questions.

  • 0 in reply to Kedar Manishankar
    TI__Mastermind 24075 points

    Also refer to the datasheet Equation 2 for the calculation to set the charge current. Maybe that is where the confusion is coming from.