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Maximum acceptable cable length between electronic board and its antenna.

gianluca peterle
Intellectual 475 points
Other Parts Discussed in Thread: BQ51021, BQ51020, BQ25100, BQ51025, BQ24250, BQ51051B, BQ51050B

For space reason in my application, I need to connect the antenna to his corresponding device, BQ51021 with a cable of  7 m long, does't work?

  • 0
    TI__Genius 14890 points

    Gianluca,

    I have used several cm, but never 7m.  The concern I have is the resulting series resistance.  I'd be concerned that the loss in the 7m cable would be too great to get any power transfer.  Do you have the resistance for the coil you would propose to use?  Do some calculations to determine the drop between the antenna and the bq51021.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Intellectual 475 points

    Hi Dick, I don't have fixed the right BQ, I am a little confused.

    I need to recharge 2 Li batteries (3,7V each) for total 7,4V, I think BQ51020 or BQ51021 are the only choice because their voltage is greater than 7,4V, isn't?

  • 0 in reply to gianluca peterle
    TI__Genius 14890 points

    Gianluca,

    The bq51020 and bq51021 can definitely reach the voltage level you need.  What is the charging current?  Both are limited to 5W.  The bq51021 adds and I2C interface.

    We are close to releasing the bq51025 which is a 10W receiver when paired with the (also soon to be released) bq25100.  The bq51025 can be set to 10V.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Intellectual 475 points

    I don't know the charging current because I don't know what I find as AA Lithium batteries on the market and their electrical carachteristics, but Dick let me ask, the BQ51020 can directly charge Lithium batteries or I have to use BQ24250 batteries charger?

    the BQ51020 have to charge the batteries and at the same time supply one electronic board, is it possible or I have to use the BQ24250 or some thing else?

  • 0 in reply to gianluca peterle
    TI__Genius 14890 points

    Gianluca,

    The bq51020 is a wireless power supply.  You will need to add a charger to the output as you suggest for the battery charging.

    The bq51050B and bq51051B are wireless power chargers for LiIon batteries (4.2V or 4.35V).

    Regards,

    Dick