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bq500212AEVM-550 / distance between Tx coil and Rx coil

Guru 29690 points
Other Parts Discussed in Thread: BQ500212AEVM-550, BQ51020, BQ500212A
Hi Team,
 
My customer has bq500212AEVM-550(Tx) and would like to know the information about vertical distance between Tx coil and Rx coil.
He considers to use bq51020 as a receiver(Rx).
Could you advise me please?
 
1)
Could you tell me acceptable vertical distance(z-axis) between Rx coil and the surface of clear plastic cover above Tx coil(bq500212EVM-550) ? I would like to know the value of min, typ, max.
 
2)
Is there any data/graph about transmission efficiency under the condition of  min-typ-max vertical distance(described above)?
 
3)
Is there any data/graph about transmission efficiency under the condition of horizontal(xy-axis) deviation from center target?
 
Best Regards,
Yaita / Japan disty 
  • Yaita-san,

    1) The standard shows that the distance between the RX coil and the TX surface is 2mm +0.5mm / -0.25mm.  The actual results of an individual system must meet these, but may work a greater distances.

    2) and 3)  We have done these types of evaluations internally with our EVMs as part of the Qi certification process.  However, they are meaningless to any system other than the EVM.  Any changes in the coil, shield, enclosure, and so on, would change the results.  Having a final system that has metal near the coil impacts the results.  Changing placement of the metal impacts the results.

    Regards,

    Dick

  • Hi Dick-san,
     
    Thank you for your prompt reply.
     
    1) I'd like to confirm the distance you mentioned  just in case. Is the following distance correct?
     
    2),3) Could you show or send me your data? I put my address below.
    My customer consider to design the system alike bq500212AEVM-550, so he would like to know the data just as a reference.
     
    Best Regards,
    Yaita
  • Yaita-san,

    Your drawing is correct.

    I have some current data, but it is not on the bq500212A EVM.  The results would be similar.  I can email you that data if you would like.

    The key points to note are that each solution in its final form (receiver or transmitter) will impact the results.  

    For the Qi certification of a receiver, testing is done at the center of the TX and 5mm from the center in 4 directions.  This allows the system to determine how the RX system would work in a normal environment.  As such, a good design has similar results at all 5 points.  

    For the Z-distance, that depends on the plastics on the RX.  Concern there it to minimize the thickness, have the proper shielding and maintain enough Z-distance for the rest of the circuitry in the system.

    Regards,

    Dick

  • Dick-san,
     
    Thank you for your precious data and advice.
    I really appreciate for your support.
     
    Best Regards,
    Yaita