• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 63 subscribers
  • Views 192 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.

BQ25798: HOW TO SET ILIM_HIZ?

Yash Dave
Prodigy 70 points
Part Number: BQ25798

Tool/software:

Our battery has a 2C rating at 2200mAh, allowing a maximum charging current of 4.4A. Therefore, which resistor settings would be suitable for the ILIM_HIZ resistor divider?

  • 0
    TI__Guru**** 166076 points

    Hi Dave,

    ILIM_HIZ sets input current limit not charge current. How much output current can your power source at VBUS provide?  We recommend that you set ILIM_HIZ clamp so that the charger does not collapse your input source.  Also, VREG*ICHG/VBUS*IBUS=efficiency. What is your VREG and VBUS?  That determines how high you can set ICHG.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Prodigy 70 points


    Our Vbus  output current provide upto 5A but we get 1A as per datsheet 1 cell battery.  and our REG is 4.2 & Vbus is 5V.

    1) Our application is based on a single-cell battery, so the parameters for a single-cell setup are already provided in the datasheet. Our system load is approximately 3A, but since a single cell can only supply around 1A, it is insufficient. Therefore, we have provided a DC-DC booster. Is the booster necessary?

    2) 

    We have understood that ILIM_HIZ limits the main input current. So, how should we design the voltage divider?

    According to the datasheet, the VILIM_REG_RNG range is 1V to 4V.

    • Is this the output of the voltage divider?
    • If so, using the ILIM formula: (VILIM_HIZ = 1V + 800 mΩ × ILIM)  If our divider's maximum output is 4V, then our ILIM would be 3.75A Correct?

    We have calculated it this way. Please confirm whether this calculation is correct or not.

  • 0 in reply to Yash Dave
    TI__Guru**** 166076 points

    Hi Dave,

    ILIM_HIZ can be tied to REGN to set the charger's max input current to IINDPM=3A.  The charger's SYS output regulates to the MINSYS voltage until the battery charges up to that voltage.  Then SYS follows the battery up to (slightly above) VREG.  So the charger's converter can provide up to 15W*efficiency to SYS output, which some of that power going to charge the battery.

    Regards,

    Jeff