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wireless power charger with bq51051B or bq51013+bq24040

Tobias Schmid1
Prodigy 30 points
Other Parts Discussed in Thread: BQ51051B, BQ51013, BQ24040, BQ51050B, BQ51003

Hi,

1.) i want to design a wireless power charger for a 3,6V battery with 45mAH capacity. For this i want to use either    'bq51051B' or 'bq51013+bq24040'. What is the better solution or do you have any other recommendations?


2.) Is it better to place the LED D1 to the BAT or RECT output?

Kind regards

Tobi

  • 0
    TI__Genius 14890 points

    Tobi,

    1)  Can you give me more information about your battery?  The bq51051B is a 4.35V Li-Ion charger and the bq51050B is a 4.2V Li-Ion charger.The bq24040 is also a 4.2V charger.  I am not aware of a 3V charger IC.

    2)  The charge indicator LED (D1 in most drawings) can be tied to either RECT or BAT (OUT).  Neither pin has a stronger reason than the other to be used.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 30 points

    1.) Enclosed you will find the datasheet from the battery.

    5123.252279-da-01-en-KNOPFZELLENAKKU_LITHIUM_LIR2032.pdf

    I think i can charge this battery with the bq51050B or not?

    2.) But the RECT outout voltage changes frequently or is it constant?

    Regards

  • 0 in reply to Tobias Schmid1
    TI__Genius 14890 points

    Tobi,

    1)  I have not seen this battery before.  Based on the charge characteristics, the bq51050B can charge the device.  My only concern is the low charge termination current.  The battery is a 40mAh battery and the spec calls for a termination current of 0.05C (which is 2mA). I have demonstrated this in the lab, but overall the accuracy of termination is not expected to be very tight.  What is the timing of your product?  In your original post you mentioned the bq51013 + bq24040.  I would suggest the bq51003 instead of the bq51013.  We have another charger in development that seems would be a better fit than the bq24040.  The timing of your project can help determine if the new product would fit.

    2)  Yes, RECT will move.  But at the current levels you require, it will not move much.  I looked at it on a single bq51050B EVM this morning and it was less than 50mV.  And BAT on the bq51050B will move as well during the fast charge portion of the charge cycle.  Depending on the battery charge state, this may move more than RECT.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 30 points

    Hi,

    1.) I want to finish my project next month and my PCB layout next week. So i think i will try it out with the bq51050B, because my PCB space is quite limited and the solution with reciever+charger in one IC will be better.

    Do you know or can you pre-estimate when the new charger will be on market?

    2.) 50mV moving will be no problem, do you know the voltage of RECT? When i tie LED to RECT, the LED will be just ON when i get power from the transmitter and when i tie it to BAT, LED is always connected with battery and ON, or am i wrong?

    Regards

  • 0 in reply to Tobias Schmid1
    TI__Genius 14890 points

    Tobi,

    1)  The new charger is planned for August 2014 release.

    2)  For the bq51050B, the RECT will stabilize during charge a few hundred millivolts above BAT.  The LED is only on when the device is in active Charge (CHG/ is low).  The pull-up being RECT or BAT has no impact on the state of the LED (aside from supplying the power if it is on).  Choosing RECT or BAT will not change when the CHG LED is on.

    Dick