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Modulation index of communication signal for reliable operation

Sean Can
Prodigy 70 points
Other Parts Discussed in Thread: BQ500210, BQ51013A, BQ51050B

Hi,

I am using BQ51013A as the RX solution and bq500210 as the TX solution. I am trying to understand the communication part better so as to make my charging platform more robust in presence of stray fields. I have a few questions regarding the same,

1. Could you please specify the acceptable modulation index of the communication signal (as seen at COMM+ pin in the TX chip) to ensure a reliable analog ping and power transfer phase.

2. COM1 and COM2 capacitors ( at RX side) affect the modulation index, what is the maximum value of these capacitor that can be used?

Thanks,

Sean

  • 0
    TI__Guru* 75866 points

    The depth of modulation can be increased to improve reliability of communications.

    Com1 and Com2 capacitors are typical 22nF but we have tested and operated with up to 68nF.

  • 0 in reply to Bill Johns
    Prodigy 130 points

    Hello Bill,

    the description of the communication caps in the datasheet of the bq51050B are confusing me a little bit. on page 17 it says something like each of the caps is 47nF and when the comm-FETs are closed there is effectifely a 22nF capacitance added to the coil. But in the schematic two 22nF caps are used for the load modulation. Could you please give me a little explanation?

    Kind Regards

    Manuel