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Original question:

BQ2057W: Unexpected battery float voltage in BQ2057WSN charging Circuit and battery not charging

BQ2057W: Application design using BQ2057W to recharge 8.4V Li-Po battery

Waleed
Prodigy 90 points
Part Number: BQ2057W

Hello,

I was looking for a solution for battery charging solution to be integrated with our design.

I found that bq2057W could be a very good solution.

 

I hold two questions :

  • Is there any typical application where I can feed 9V source to recharge the 8.4 battery? Is this schematic is valid?

 

  • Can I ommit the temperature part by connecting the TS pin to 50% of Vcc (9/2)= 4.5V as it will lie between 30.9% and 61.8% of the Vcc?
  • What is the recommended schottky diode? Does it depend on the charging current of the battery?

I created a design based on the datasheet. However, I hope you can correct any values (like the driver R4 resistor if needed to be changed).


Thanks

  • 0
    TI__Guru* 75806 points

    Hello

    Is there any typical application where I can feed 9V source to recharge the 8.4 battery? Is this schematic is valid? --- Bill J -- 9V may not be enough due to voltage drop in sense resistor, pass transistor and diode.  Also Connectors will have some voltage loss.  The schematic is valid.

     

    Can I omit the temperature part by connecting the TS pin to 50% of Vcc (9/2)= 4.5V as it will lie between 30.9% and 61.8% of the Vcc?---Bill J -- Yes a fixed voltage divider can be used.  But thermal protection of the battery is recommended.

     

    What is the recommended schottky diode? Does it depend on the charging current of the battery? -- Bill J -- This is to prevent revers current flow.  You would want to look for low forward voltage drop at your max charging current.

     

  • 0 in reply to Bill Johns
    Prodigy 90 points

    Thank you Bill so much for answering all of my questions.

    Is 2 kohm enough for the LED Stat indicator or does it depend on Vcc voltage?

    Also would 12V be OK or it will result that the STAT LED would never turn off ?

     

     

  • 0 in reply to Waleed
    TI__Guru* 75806 points

    Hi Waleed

    I think 2k resistor will work for the LED but it will depend on the LED current.  Max current out of the STAT pin should be limited to 10mA.