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BQ24650: BQ24650 Output Voltage Is 0.78V

Dharmesh PAtel
Prodigy 240 points
Part Number: BQ24650

Hello Community,

Im Using the BQ24650 MPPT battery charger for my MPPT application.

Here is my test point voltages are as follows:

REGN: 6V

BTST: 6V

PH:0.78V

MPPT:1.23V

TS:1.9V

VREF:3.29V

HIDRV:0.78V

LODRV:0V

As per the datasheet im getting all pins voltage correct except HIDRV,LODRV and BTST Can you please suggest me the possible solutions for this issue.

Thanks & Regards

Dharmesh Patel

  • 0
    TI__Mastermind 24075 points

    Hi Dharmesh,

      Can you take a scope capture of HIDRV, LODRV, and PH? These pins switch voltage levels so measuring DC value would not be accurate. Please how the BQ24650 portion of the schematic so I can take a quick look.

  • 0 in reply to Kedar Manishankar
    Prodigy 240 points

    Hello,

    Thanks For Your Reply,

    I Dont have scope for measurements,

    Here im sharing my design schematic file.

    Please review it , suggest me any possible solution for this.


    Thanks & Regards
    Dharmesh Patel

  • 0 in reply to Kedar Manishankar
    Prodigy 240 points

    Hello Kedar Manishankar,

    The issue for 0.78V output has been resolved by replacing the BTST pin resistor.

    The Recommended value for BTST pin resistor is 2.2 Ohm but during assembly by mistake the resistor 980 Ohm has been solder, after replacing BTST pin resistor Im getting the desired output 4.51V.

    Now im facing the new issue which is during the absent of battery my charging voltage is 4.51V when i power up my device, Now as i disconnect the supply and plug my battery and than turn on my device my charging voltage is 0.67V which is very strange scenario.

    Sometimes the charging has been started and charging status LED turn on but the charging current is only 0.28A which is not desired charging current that i want

    Also the During charging My both Switching MOSFET will shorted and system gets stop working!

    I dont know why both HIDRV and LODRV MOSFET gets shorted.

    Can you please help me with this.

    My Pin Voltages are as Follow:

    VCC:20V

    MPPTSET:1.21V

    TS: 1.61V

    REGN:6V

    Please suggest me any solution!!

    Thanks & Regards

    Dharmesh Patel

     

  • 0 in reply to Dharmesh PAtel
    TI__Mastermind 24075 points

    Hi Dharmesh,

       Shorting across the MOSFET does not occur because of the charger operation. As this is a charge controller and you have choice of schematic and layout, the issue will most likely be there. What voltage of your battery are you plugging in?

    MPPSET pin = 1.2V indicates that the charger is operating in the input voltage regulation loop. This means the load on your input supply is causing the input voltage to droop. Are you measuring VCC close to the pin of the IC?

  • 0 in reply to Kedar Manishankar
    Prodigy 240 points

    Hello Kedar Manishankar,

    My Li-Ion Battery rating is 3.6V, which fully charged voltage is 4.2V and im setting the charging Voltage of 4.5V.

    The VCC pin voltage is aroung 19.8V.

    The MOSFET that i choose will be okay or not?

    Also im confused: During the charging is in progress if i remove the battery this will cause the MOSFET damage?

    Thanks & Regards

    Dharmesh Patel.

  • 0 in reply to Dharmesh PAtel
    TI__Mastermind 24075 points

    Hi Dharmesh,

       No, removing the battery during charging will not cause an issue. Neither will shorting the battery to GND, as we have inbuilt protection against that. Why are you setting the charge regulation voltage of the IC so much higher than the actual max charge regulation voltage of your battery? This could be dangerous. You are supposed to set it to 4.2V if the max charge regulation voltage of your battery is 4.2V.