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BQ25792: BQ25792 Battery Charging Problem

KO JAESUNG
Prodigy 20 points
Part Number: BQ25792


Tool/software:

Hello,

I have designed a circuit using the BQ25792 IC to charge a lithium polymer battery and supply power to the system through the voltage output from the SYS pin. However, the battery is not charging, although the output voltage at the SYS pin is normal. Could you please review the circuit?

  1. No operation I2S.
  2. D + and D- pins not used. 
  3. VBUS Input voltage are 15V 
  4. SYS Pin output are 7.2V
  5. The PROG BAT , 2S and 1.5MHz (li-polymer battery , Nominal Voltage 3.7V)
  6. The circuit does not do any boost or buck.

Thank you.

  • 0
    TI__Guru**** 169736 points

    Hi Jaesung,

    I do not see any obvious issues with the schematic.  Is STAT pin blinking?  What do the status and fault registers from REG0x1B to 0x27 report?

    Regards,
    Jeff

  • 0 in reply to Jeff F
    Prodigy 20 points

    Hi Jeff,

    Thank you for reviewing the circuit. After changing the voltage divider resistor values on the TS pin to 6.8kΩ on the top and 10kΩ on the bottom (confirming approximately 3.0V at the TS pin), charging is now starting, and the STAT LED indicates proper operation. However, when the current limit on the ILIM_HIZ pin was set to 1.5A (using 127kΩ/100kΩ resistors), charging only lasted for about 5 seconds. After adjusting the charging current to approximately 0.8A, charging is now proceeding normally. Currently now, I am considering heat dissipation PCB design due to the high heat generation when using the system pin output simultaneously with charging. , Thanks a lot

  • 0 in reply to KO JAESUNG
    TI__Guru**** 169736 points

    Hi Jaesung,

    TS pin at 3.0V is likely JEITA cool which would reduce charge current.

    Regards,

    Jeff