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LDC1614-Q1: Optimizing the Rp parameter

Shinji Tsuji
Genius 13409 points
Part Number: LDC1614-Q1
Other Parts Discussed in Thread: LDC1614

Hi team,

I am optimizing the resolution of the distance measurement using LDC1614 with 10mm diameter circular coil.

I have a question about the parameter Rp. Is there optimal range of Rp in terms of the resolution?

regards,

  • 0
    TI__Genius 17440 points

    Hello Tsuji-san,

    The Rp does not directly affect the resolution. However, it does affect the sensor oscillation amplitude, which can negatively impact the resolution if the oscillation amplitude is outside of the recommended range. As long as the sensor oscillation amplitude is between 1.2V - 1.8V, the Rp value will not affect the resolution. In some inductive sensing systems, the Rp value can change so much with target interaction that no single IDRIVE setting will keep the sensor oscillation amplitude within the optimal range. Outside of the optimal amplitude range, the resolution will reduce. The resolution will also reduce if multiple IDRIVE settings are used, because this can introduce an offset in the digital output codes. In these cases, it's sometimes helpful to add a parallel resistor to the LC tank.

    In general, once the outer coil diameter has been maximized, I recommend designing for a high Rp value. The spiral inductor designer in the LDC Tools Excel Calculator is a good way to experiment with the Rp value. The tool's estimated Rp value can be mapped to the IDRIVE settings in table 39 in the datasheet.

    Best Regards,

  • 0 in reply to Kristin Jones93
    TI__Genius 13409 points

    Hi Kristin,

    Thank you for your answer.

    >I recommend designing for a high Rp value.

    Why do you recommend to design high Rp value after you select the maximum coil diameter?

    regards,

  • 0 in reply to Shinji Tsuji
    TI__Genius 17440 points

    Hi Tsuji-san,

    The outer coil diameter is the most important sensor characteristic for sensing range and resolution. The Rp value is the next most important characteristic. A high Rp sensor requires less current to drive it, which reduces the current consumption of the system. It also gives more flexibility in the drive current settings listed in Table 42 of the datasheet. This makes it less likely that the system would need multiple drive current settings.

    Best Regards,