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LDC2114: Threshold value for on detection

Steve Roe
Prodigy 50 points
Part Number: LDC2114
Other Parts Discussed in Thread: LDC2112

Hi, I am using LDC2114 for a application which is detecting a series of pulses.

We wanted to use the on-chip TTL Logic output to determine when we pass each peak to simplify our firmware development.

However the value of inductance for the Threshold is near the valley of our signal which is not idea for accurate peak detection.

Is there a way to change the threshold value used by the chip to determine when a peak ( ie button) has been passed (pressed)?

Thanks,

Steve Roe

  • 0
    TI__Genius 17440 points
    Hi Steve,

    It is possible to change the threshold using the Hysteresis register. Section 8.1.8 of the datasheet, "Setting Button Triggering Threshold," explains how to use the Hysteresis register to set both the on-threshold and off-threshold.

    Regards,
  • 0 in reply to Kristin Jones93
    Prodigy 50 points
    Hi Kristin,

    thanks for your answer. This hysteresis is a nice feature.
    We want to move the nominal button triggering threshold of 128
    We would still need to allow for hesteresis around the new higher setpoint to accurately determine the peak levels.
    Inductance levels of our peak are around 1000 counts, should we try lower inductance coil / targets combination or is it possible to set the triggering higher than 128?
    Thanks,
    Steve
  • 0 in reply to Steve Roe
    TI__Genius 17440 points

    Hi Steve,

    The nominal button triggering threshold is fixed at 128. You can effectively reduce this threshold by using the GAINx registers (which applies gain to the net code, which is the raw code value minus the baseline tracking), but I do not think you can effectively increase the threshold. This is because our minimum gain factor is 1. If you'd like to read more about this, I recommend section 6 of the LDC2112 and LDC2114 Internal Algorithm Functionality app note.

    If you really want to reduce the value of the raw code response, you could change to a less conductive target material or increase the distance between the target and the sensor.

    Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 50 points

    Hi Kristin,

    thanks for the additional information, we will look into those options.

    Cheers,

    Steve