• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 62 subscribers
  • Views 961 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Bq5105x Revision

Adrian Alvarez
Prodigy 120 points
Other Parts Discussed in Thread: BQ51050B

Hi,

For my graduation project I need to design a wireless power charger for a 3V battery with 100mAH capacity. For this I am using the Bq5105xB and the Bq5105xB-EVM.

1) I attach my current design is there anything I can do to improve it?
- i want to know if my calculation of the Rterm is correct, is very small 2.4 ohms?

my Ibulk is 100mA, i used the 10% of this to calculate that resistanc as mentioned in the datasheet.

2) I have read some post of the forum, what do you guys mean with tune the capacitors at the receiving bank?

3) What do you recommend me for the receiver coil?

Thank you in advance

Adrian

  • 0
    TI__Genius 14890 points

    Adrian,

    A few things to consider.

    1.)  It looks like you followed the EVM schematic pretty well so you are in good shape there except for EN2.  EN2 is used if you are planning on a wired charger that would operate in conjunction with the bq51050B.  In this case I suggest you tie EN2 to the OUT pin.

    RTERM needs to be changed.  Equation 2 in the datasheet shows:  RTERM=KTERM*%IBULK.  For 10%, the factor is 10, not 0.1.   In that case, the equation is RTERM = 240 * 10 = 2.4k Ohms

    2)  The 3 capacitors in series and 2 in parallel with the pick up coil in your schematic are what is used to tune the system.  See the section of the datasheet titled "Series and Parallel Resonant Capacitor Selection" in the datasheet.  If you are building a system that will perform like the EVM (with a coil suggested in section 3) the default values you have may be sufficient.  I would definitely use 3 capacitors in case you need to tweak the values once your board is built.

    3)  The bq51050B EVM User's Guide has 3 coils that have been verified on the EVM.  Please seen the Bill of Materials section on page 20.

    A few more things to consider.

    If you are using a commercially available transmitter, I would suggest a Qi-compliant version.

    When selecting capacitors, make sure you choose the correct voltage rating.  Some of the pins can see very high voltages.  Note the Absolute Maximum table in the datasheet for values that can be seen.  Use the EVM Bill of Materials section for another idea of the ratings.

    Investigate NP0 (C0G) and X7R capacitors for best results.

    The bq51050B is optimized for higher current uses (1A for 5W).  It will work quite well at your 100mA charging current.  You must be aware that the accuracy of the termination current will not be precise.  You should expect a wide variation to the 10mA you desire.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 120 points

    Dear Dick,

    That helps a lot thank you for your answer.

    Kind regards,

    Adrian