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Power converter for Handheld device

Vishwanath G
Intellectual 270 points
Other Parts Discussed in Thread: BQ25619, BQ25616, BQ25886

Hi,

I am working on health monitoring device, which is portable and handheld. We are suppose to use Li-Po battery. I am bit confused whether to use single 3.7V single Li-Po battery or to choose series of 2 3.7V battery. Kindly suggest which topology is better with great efficiency (example boost or buck boost or only buck). I have searched buck-boost ICs in TI, found some difficulty for 3.7V range.

Device working voltage is 3.3V and current consumption is around 1.5 amps.

thanks,

Vishwanath G

  • 0
    TI__Guru**** 165766 points

    Hi Vishwanath,

    The smaller the difference between the input and output voltages for any dc converter or charger, the higher the efficiency is.  So, if you plan to charge from a 5V power source, then the charger will be most efficient with a single LiIon charger.  Also, if you system electronics are all close to 3.3V, the same applies. For charging, I recommend the BQ25619 if you have I2C communication available or BQ25616 if not.  For buck boost ICs, I recommend searching the TI website for TPS63XXX devices.  TP630242 might work for you.

    Regards,

    Jeff 

  • 0 in reply to Jeff F
    Intellectual 270 points

    Thanks Jeff,

    Due to some constraints I have planned to use BQ25886 in standalone mode and almost finalized. I have few questions in that device, (since I am using 2 3.7V Li-Po batteries in series.)

    1)  Pin 15 & 16 SYS (System Connection), is it output voltage that can be given to my electronics? ( I hope this is not my Li-Po battery charging voltage).

    2) If I power my electronics directly from the battery and use up to battery minimum voltage around 6V any impact on IC? or is it mandatory to use SYS pin function in case it is dedicated to load electronics, if I am right?

    please do the needful.

    thanks,

    Vishwanath G

  • 0 in reply to Vishwanath G
    TI__Guru**** 165766 points

    Hi Vishwanath,

    Regarding 1, yes, the SYStem load is attached at the SYS pin.

    Regarding 2, if you attach the load at the battery, you lose the 2 benefits of power path (having a SYS pin):  accurate charge termination and power up with discharged battery at plug in.

    Regards,

    Jeff

  • 0 in reply to Jeff F
    Intellectual 270 points

    Thanks Jeff,

    your answers and suggestions helped me alot. thank you.

    Vishwanath G