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LDC2114: turn on and calibration

ben pescud
Prodigy 60 points
Part Number: LDC2114

When a metal target is directly against the coil as the LDC2114 is powered up we notice that the behaviour of the sensor output changes.

The sensor output sensitivity is now very large, so that the sensor output is -2048 if the metal target is not present and 2048 if the coil is present, the baseline tracking dose not appear to be functioning even when left at a negative value for a long time.

is there an application note or any data describing the initial turn on and calibration of the IC? (besides "Figure 21:Power-On Timing" in the datasheet)

 

  • 0
    TI__Genius 14270 points
    Hello Ben,

    When the LDC2114 starts converting (after powering on or after a device reset), it sets its internal baseline. The expectation is that the metal target only moves a small distance relative to the position of the sensor. If you have large movements of the metal with respect to the sensor, you may overrange or underrange the inductive measurement.

    You need to set the channel GAIN setting based on the amount of movement that the metal will see. The rate at which the LDC adjusts to sensor changes is set by the NPBI and LPBI (normal power and low power base increment) - a higher value allows the LDC to track larger shifts faster.

    If you completely remove the target while the LDC2114 is operating, then it can take a significant amount of time to return to normal operation if the GAIN is set to a higher value and the NPBI/LPBI are set to low values. This is discussed in section 8.1.9 of the LDC2114 datasheet.

    It is important to set the SENCYC and LCDIV settings based on the sensor frequency, as discussed in section 8.1.6 of the datasheet. If the sensor frequency is significantly different (typically you have a range of about +/- 35% from the nominal setting), then you can overrange or underrange the measurement.

    Regards,

    ChrisO