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Flex PCB coils

Thorsten Brandt
Prodigy 110 points

Hi,

is there a chance / a way to implement the coils of the RX and TX side in form of two flex pcbs  (1, 2, 4 or if inevitable 6/8 layer) with (different) layouts for the coils ? 

What would you recommend for the dimensions of the coil (diameter, n, ...)

Could we omit the ferrites ?

  • 0
    TI__Guru* 75656 points

    Hi

    The transmitter coil is well defined by the WPC standard and there is little flexibility.  TI is not supporting a single coil PCB version at this time.  The coil type B2 is a multi coil PCB design.  But ferrites or shields will be required. See FAQ post on the forum and link to WPC standard section 1.

    The standard does allow a great deal of flexibility for the receiver design and flex pcbs are possible.  Shields are typical required for satisfactory performance.  

    But the trade off you will see when going to a PCB coil is lower efficiency due to higher resistance of traces vs copper wire. 

    Coil dimensions will depend on your requirement and application.  If the receiver coil is the same size and shape as the TX coil you will have the best performance, about 45 mm round coil.  But the bq51013EVM-725 uses a 40mm X 30mm coil with good performance up to 1A.  For lower power applications 500mA or less a physically smaller coil may work well, Mingstar 312-00015 is a 28 X 14 mm coil.

    Best Regards

    Bill