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BQ24133: Can a 9 V be used for VBUS be used to charge a 2S1P Battery?

Victor Salomon
Expert 3910 points
Part Number: BQ24133
Other Parts Discussed in Thread: , BQ24610

Hello team,

I am supporting an application using BQ24133, the project will have a 2S1P Lithium-Ion battery and has a voltage source of 9.0 V, the guide for the evaluation module (BQ24133EVM-715-15V) mentions that the supply for charging needs to be at least 1.0 V above the maximum battery voltage (which would be 8.4 V in this case), but I couldn't find the same mention on the BQ24133 datasheet.

Q: Is it possible to use a 9.0 V source to charge a 2S1P Li-Ion battery to maximum charge (8.4 V)?
Q: If so, What design considerations should be taken?

  • 0
    TI__Intellectual 1980 points

    Hello,

    Need to increase the supply voltage. 9V is not OK to charge 8.4V battery. Recommend increase to higher than 9.4V.

    You will have voltage drop between supply voltage and charger's VIN pin. Also, think about dead time of BUCK, and rise time of MOS. The duty cycle is too high if convert 9V to 8.4V.

    Regards.

  • 0 in reply to Kerry Song
    TI__Expert 3910 points

    Hello Kerry,

    Thanks for your feedback. Is there any documentation on the bq24133 datasheet that points out the minimum supply voltage for a 2S1P configuration?

    Also, If a 9.0 V supply for a 2S1P configuration (with a max. charge of 8.4 V) is not enough, such as in this case, what other solution or part would you recommend instead of bq24133? (given this system is limited to a 9.0 V supply)

  • 0 in reply to Victor Salomon
    TI__Intellectual 1980 points

    Hello,

    It is BUCK knowledge. Generally, duty cycle should be less than 92%. Reason is that: for example, dead time 30ns, rise time and delay time of 2 MOS 13ns. Frequency 1.6M, period 625ns. You could calculate and get the result, nearly 93%. Also, you should have voltage drop between power supply and VCC pin.

    No part can convert 9V to charge 8.4V battery.

     

    Regards

  • 0 in reply to Kerry Song
    TI__Genius 14410 points
    Hi Victor,

    For Buck mode charger, there is no part can meet this requirement. Could you provide more information of customer design? If customer really wants to use 9Vin, I think only our Buck-Boost charger could meet this requirement but it is maybe overkill to customer design.

    Thanks,
    Ann Lien
  • 0 in reply to Ann_Lien
    Expert 1220 points
    Hi Sir,

    In my application use stand along charger bq24610.
    600kHz fsw can met 9.0 V supply for a 2S1P?
  • 0 in reply to Wen Yung
    TI__Genius 14410 points
    Hi Wen,

    For bq24610, period is 1666ns and deadtime is 60ns. But bq24610 is with output MOSFET, rising/falling time would be relatived to gate drive layout, MOSFET spec. Please verify your board layout and MOSFET gate drive condition and calculate the maximum duty cycle. But according to real application and margin, we still recommend use higher input voltage.

    Thanks,
    Ann Lien