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Original question:

BQ25176MEVM: Is max operating input voltage 6.6 V?

BQ25176M: Does this IC work at 15V?

Andres Sabas
Prodigy 20 points
Part Number: BQ25176M

Tool/software:

Hi team,

I'm having an issue with the BQ25176M in my circuit. It only delivers the programmed charge current (500mA) within a narrow input voltage range (Vin = 5V to 6V). As I increase the input voltage further, the charge current drops significantly, and the IC eventually stops charging my 1S 3.7V Li-Po battery.

Components:

  • Li-Po battery: 1S 3.7V
  • Riset: 604Ω
  • VSet: 18.2kΩ
  • Expected output:
    • Iout = 500mA
    • Vout = 4.35V

I have the following questions for you:

  • Is the datasheet information regarding the input voltage range (up to 18V) inaccurate?
  • Are there any additional components required for proper operation at a 15V input voltage?

 

I look forward to hearing from you.

  • 0
    TI__Guru* 75676 points

    Hello

    The BQ25176M has thermal regulation that will reduce output current to manage device temp.

    As input voltage is increased the power dissipation increased and more likely that thermal regulation will start.

    Check the votlage on ISET pin, should be 1V when in current regulation at target value but will drop when thermal regulation starts.

  • +1 in reply to Bill Johns
    Prodigy 20 points

    Hello Bill,

    We have done some tests to analyze the charging behavior of the BQ25176M IC below are the parameters used and the results.
    Vout= 4.35V Ichrg= 800 mA
    RVset= 18k
    RIset=390

    Results with Battery Connected:

    • Vin = 5.06V, VRIset=1.13V, Ichrg = 750 mA, VBat=3.55V.
    • Vin = 6.02V, VRIset=0.578V, Ichrg=360 mA, VBat=3.473V
    • Vin = 7V, VRIset=0.42V, Ichrg=250 mA, VBat=3.44V
    • Vin = 8V, VRIset=0.3V, Ichrg=190 mA, VBat=3.424V
    • Vin = 9.02V, VRIset=0.24V, Ichrg=150 mA, VBat=3.414V
    • Vin = 10.01V, VRIset=0.2V, Ichrg=120 mA, VBat=3.406V
    • Vin = 12V, VRIset=0.16V, Ichrg=90 mA, VBat=3.398V
    • Vin = 15V, VRIset=0.12V, Ichrg=60 mA, VBat=3.393V

    After all these tests we get unsatisfactory results since our supply voltage tends to be between 8 and 15V, but the charger does not work throughout this range.

    Are there any additional settings we can add to make it work or any additional recommendations?

    Attached is the image of the schematic used and the PCB circuit.

    PCB circuit

  • +1 in reply to Andres Sabas
    TI__Guru* 75676 points

    Hi Andres

    This look like thermal regulation.  The charge current is reduced as Vin increases, battery will charge but take longer.

    Changing the layout will improve the power dissipation and increase output current in the 6V to 8V range.

    A switching converter would provide more current over this range.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    I understand, but I need an IC that allows an input range between 4V to 15V, could you recommend some of these?

    The input range will be provided by solar cells, thanks in advance!