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LDC5071-Q1: connecting two ASICs to the same excitation coil

Victor Zhitomirsky
Prodigy 110 points
Part Number: LDC5071-Q1

Tool/software:

Most ASICs designed for metal target inductive sensors allow for connecting two chips to the same excitation coil. Each sensor can measure its own set of receive coils. For instance, one set can be configured for a fine scale and another for a coarse scale. Can two LDC5071 parts be connected to the same pair of capacitors and the same single excitation coil? Additionally, do we need to use four resistors, approximately 10 Ohms each, on the LCin and LCout pins of each LDC5071 to isolate them? Thank you! Any feedback would be greatly appreciated.

  • 0
    TI__Mastermind 40295 points

    Victor,

    Two LDC5071 devices cannot share a single excitation coil.
    Each device requires its own set of coils.

    Note that the two exciter oscillation waveforms will tend to synchronize when the two coils are located near each other and are sharing a target.

    You can certainly use small resistors between the coil and the LCin and LCout pins, but they usually aren't necessary.

    Redars,
    John

  • 0 in reply to John Miller - Sensing
    Prodigy 110 points

    Thank you, John.

    Could you please double-check your answer? I assume that the implementation of the oscillators on your LDC5071 is quite similar to that of competing ASICs. We know competitors allow using a single TX coil shared between two oscillators in two ASICs. It would be disappointing if we could not switch to using your much cheaper LDC5071 due to the implied hardware differences.

    Best regards

    Victor

  • 0 in reply to Victor Zhitomirsky
    TI__Mastermind 40295 points

    Victor,

    I share your disappointment and can say with certainty the LDC5071 will not support a single exciter coil shared between two devices.

    The device is based on a core which predates the market's interest in shared coils.

    New devices will support this use-case.

    Regards,
    John