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BQ51013B: Start up problems with some TX

Sander Kolkman
Prodigy 20 points

Hello John,

Thanks for your reply, I have another question. We use a PCB coil as a RX coil. This coil has a high induction so our series capacitor is calculated at 32nF. We dont use the parallel capacitor. Our Ccomm capacitors are 47nF. This worked for a long time on some different TX pads. But now we have a problem that our circuit doesnt work on many TX pads. Do you think that the 47nF capacitors on the Ccomm pins are correctly chosen with the series capacitor of 32nF on the coil?

Best regards,

Sander Kolkman

Post Split off from:

BQ500212A: Alternative for the BQ500212A.

  • 0
    TI__Guru* 75906 points

    Hi Sander

    PCB coil are difficult and I do not recommend them. 

    If yours was working and has changed some things to check on:

    1.) Changes in PCB runs or vendors that can a shift in coil shape / L and tuning. Do older PCBs still work?

    2.) You should have shielding behind the coil protecting battery and PCB from AC field -- has vendor size or placement changed?

    3.) Comm capacitor value --- typical value is 10% to 20% of the tuning (series cap) value, it can be higher.  In your case it is much higher and than could be a problem.