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BQ51221 range between primary and secondary coils

Majid Safari
Prodigy 145 points
Other Parts Discussed in Thread: BQ51221

Dear Dick

What is the efficient distance between primary and secondary coils using BQ51221 device? (Using off the shelf transmitters)

Are there any other receiver coils on flex PCB which are suitable to use with BQ51221 and support both WPC and PMA? (Like what is fitted on the back of mobile phones like Lumia) Do you have any part number or manufacturer name in mind?

I look forward to hearing from you.

Kind Regards,

Majid

  • 0
    TI__Genius 14890 points

    Majid,

    The detailed specifications for the Transmitter and Receiver spacing can be found at the WPC website.

    Briefly, the space between the TX coil and the surface is 3mm.  The space between the RX coil and the surface is 2.5mm.  Of course, both have tolerances.

    We have had good results with the Dexerials flexible coils. You would have to discuss specific details on the coils with them.  If you need more details, let me know.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 145 points
    Dear Dick

    Thank you for detail information.

    I have checked the Dexerials flexible coil products and they look great. I can use either of these products: (fortunately I have enough room)

    NSTC3030T7046-18A, NSTC4030T7536-18E, NSTC4440T5228-18A and NSTC4832T7346-16B (this one has the lowest inductance so maybe is more suitable for BQ51221).

    My question is which one you have experience with?

    I am asking this question because if you already have tried them you may (I thank you in advance) share some information in regards to:

    1. Cs (C1) value (I have tree place holders)
    2. Cd (C2) value (I have two place holders)
    3. Ccomm1 & Ccomm2 values
    4. Cboot1 & Cboot1 values
    5. Cclamp1 & Cclamp2 values

    Finally, my last question, have you checked them with a PMA power transmitter?

    I look forward to hearing from you.

    Regards,
    Majid
  • 0 in reply to Majid Safari
    TI__Genius 14890 points

    Majid,

    I used the 4832-16B.  I have not run this with the bq51221 in PMA mode. 

    The Ls = 10.9uH, Ls' = 13uH with the ideal Cs = 195nF and Cd = 2.35nF (based on 190nF for Cs).

    See the bq51221EVM-550 User Guide for COMM, BOOT and CLAMP capacitor value recommendations.  

    PMA requires a lower coil inductance than WPC.  Choosing one for a dual mode needs to take this into account.  Characterization of the coils in your system is very important as the Ls' will change.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 145 points
    Dear Dick

    Thank you for the suggestions.

    In regards to bq51221EVM-550, I think you meant bq51221EVM-520.

    Cheers,
    Majid
  • 0 in reply to Majid Safari
    TI__Genius 14890 points

    Majid,

    Thank you, yes, it is the bq51221EVM-520.

    Were you able to acquire the coil you were investigating?

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 145 points
    Dear Dick

    Thanks for asking. Yes, I am in contact with one of the Dexerials's sales person and I am waiting on the samples to be arranged for shipment.

    Cheers,
    Majid