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BQ25820: question about the mode of operation

Martin Sauer
Prodigy 150 points
Part Number: BQ25820

Tool/software:

Hi,

I want to use the BQ25820 to charge a LiPo accu with a solar cell and supply the board.

The solar cell provides 5V with 2-4W. The akku is a LiPo 3,7V with 27Ah. The system voltage is 3,7V.

If the solar cell powers the device, Q1 and Q2 are open. To supply the system Q3 has also be open. If both MOSFET are open how will be the system voltage regulated? I read the datasheet, bu I don't understand the theory of operation. 

Can you help me.

BR

martin sauer

  • +1
    TI__Mastermind 32941 points

    Hello Martin,

    Martin Sauer said:
    If the solar cell powers the device, Q1 and Q2 are open. To supply the system Q3 has also be open. If both MOSFET are open how will be the system voltage regulated? I read the datasheet, bu I don't understand the theory of operation. 

    Q1,Q2,Q3 can not be open at the same time.

    If adapter/reliable solar cell is present Q1/Q2 are open and the system voltage is the same as the adapter voltage.

    If adapter is not present, Q3 is open and battery is supplying power to system, and system voltage is slighlty higher than battery voltage.

    Best Regards,

    Christian.

  • 0 in reply to Christian Moyer
    Prodigy 150 points

    Hi Christian,

    thanks for your answer. However, the data sheet describes

    That both FETs are active. Is this a mistake then?

    BR

    martin

  • 0 in reply to Martin Sauer
    TI__Mastermind 32941 points

    Hello Martin,

    Martin Sauer said:
    That both FETs are active. Is this a mistake then?

    This is not a mistake, the wording is just a little confusing, please refer to my previous comment on when the BATFET/ACFETS are active. They are not active at the same time.

    Best Regards,

    Christian.