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BQ24075RGTT Charger

pranavp
Prodigy 140 points
Other Parts Discussed in Thread: BQ24075

Hi,

I have built this charger circuit. I am facing issue in battery charging. When main supply and li-ion battery (3.7V) is connected then CHG indication (pin 9) goes low (led turns off) and when battery removed pin9 goes high(led turned on). Battery is neither fully charged nor fully discharged.

When i connect battery alone i get proper voltage at output, but if i connect main supply momentarily and then remove it i get 3.3V from the battery.. I would really appreciate if some one can help me out.. i think battery is not charging.

I have used R1=R2=1.5K

Thanks

  • 0
    TI__Mastermind 32350 points

    Hi,

     

    You need a resistor in LED before connecting to both pin 9 and 7. Please verify your schematic with the user’s guide EVM schematic.

    http://focus.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slvu274c&fileType=pdf

    Thanks!

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 140 points

    HI

    thanks for the information.

    I have added the resistors with led

    just for checking i have removed the old chip and soldered a new one, now i am getting strange response.

    when i connect the main supply without battery i get 1.4 volts only at out, both the led's are off but when i connect the battery and main supply i get proper voltage at out (PGOOD turns on and CHG gets turns off within a second) and when battery is connected alone i get proper voltage. i don't know what i am doing wrong.

    Tahar I would really appreciate any suggestions.

    Thanks

  • 0 in reply to pranavp
    TI__Mastermind 32350 points

    Hi,

     

    • Did you connect your TS pin to temp sensor of the battery? For applications that do not utilize the TS function, connect a 10kΩ fixed resistor from TS to VSS to maintain a valid voltage level on TS.
    • Make sure that your SYSOFF is connected to low for normal operation.
    • Can you please try to charge up your battery using a power supply, because the protective circuitry can cause the battery to close off its terminals?

     

    Thanks!

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 140 points

    Hi,

    Thanks for your response. I charged the battery, built a new board and everything seems to work now.

    I have noticed when i connect the main dc power supply(4.5V) the chip gets heated(about 40 degree centigrade) in about 1-2 minutes at no load condition(without battery and system), is it normal?

    Thanks

  • 0 in reply to pranavp
    TI__Mastermind 32350 points

    Hi Pranav,

     

     

    Check if there is any leakage currents during that period.

     

    The operating range for this device is from -40C to 125C. If the temperature exceeds

    TJ(REG) , the device automatically reduces the charging current to prevent the die temperature from increasing further.

     

    Also, the bq24075 family is packaged in a thermally enhanced MLP package. The package includes a thermal pad to provide an effective thermal contact between the IC and the printed circuit board (PCB). The power pad should be directly connected to the VSS pin. Please see SLUA271 app note for more info.

     

     

    Thanks!

    Tahar