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LDC5072-Q1: what waveform is normal

?? ?
Prodigy 10 points
Part Number: LDC5072-Q1

Tool/software:

We've chosen this LDC5072 into our products lately.While when we test on PCBs, some issues has happened.I tryed to make an oscilloscope capture of Lcout.The pictures I taken show as below.We don't know whether it is normal,because other simple LC oscillation circuit waveform that we test on the oscilloscope is continuous. And we also wish to learn from you what is related to  ILIM_LC in this chip so that we can adjust something to meet our needs.

  • +1
    TI__Mastermind 37605 points

    It looks like the LDC may be in a FAULT state.
    When the device is in FAULT, the LCOUT will pulse on and off over a period of 5ms.
    The possible FAULTS are covered in sections 8.3.5.4 Fault State Diagnostics and 8.4 Device Functional Modes for more info.

    The first troubleshooting step should be to confirm the circuit connections and DC voltages.
    Please give that a try and let us know what you find.

    Regrads,
    John

  • 0 in reply to John Miller - Sensing
    Prodigy 10 points

    We checked our circuit connection and DC voltage.Both of them are ok.And the chip can be in a NORMAL state.

  • 0 in reply to ?? ?
    TI__Mastermind 37605 points

    Thank you for the update.

    Are you using our EVM, or are you evaluation your own design and PCB?

    Regards,
    John

  • +1 in reply to John Miller - Sensing
    Prodigy 10 points

    Sorry for missing the reply notice.Yes,we evaluation our own design and PCB.

    We tested few days and we think all is quite good for single chip.

    However, we found anther question.We want to use two LDC5072 to collect two channels angle data,and our design is showed as below. And the question is: we found if we only use one excitation coil connected to one chip for all receive coils while the other only used to receive the induced signal, the latter one can't work normally. 

    Is there any configuration about two chips for this situation or can you provide some advices?

    Regards,
    Zhipeng

  • 0 in reply to ?? ?
    TI__Mastermind 37605 points

    Zhipeng,

    The recommended way to use two devices is for each device to have its own excitation coil, and its own set of receive coils.
    This will give two complete, redundant channels.

    Regards,
    John