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[FAQ] Factors to consider when setting the baseline tracking algorithm for rapid temperature changes

Other Parts Discussed in Thread: LDC3114-Q1, LDC2114, LDC2112, LDC3114

What factors need to be considered when setting the baseline increment (NPBI or LPBI) for the LDC2112, LDC2114, LDC3114, or LDC3114-Q1?

  • There are a few different things to consider when setting the baseline increment registers for the LDC211x and LDC3114.  The rate of change for the temperature is the main impact. The faster the rate of change, the faster the baseline tracking algorithm will need to adjust to prevent a false output state. The baseline increment setting determines how much change in the baseline will occur per measurement sample obtained by the device. Because of this, the sample rate will have an impact on how well the device can keep up with temperature change over time.

    In addition to the rate of temperature change, the direction of temperature change also makes an impact. The baseline tracking algorithm has a fast tracking setting for when the baseline value goes negative. When this occurs, the baseline increment step size will be increased based on the fast tracking factor allowing it to compensate faster than when the measurement data is above 0.

    The gain of the device is applied after the baseline tracking algorithm so it does not have a direct impact on the performance of the baseline increment setting. In other words, the gain increases the impact of the temperature change as well as the baseline increment. Because of this, gain can be used to control the feel of the button press while having minimal impact on the temperature compensation.

    The last consideration for setting the baseline increment is the use case of the design. You should consider when the buttons will be pressed in relation to the temperature change. If the button is pressed while the temperature is decreasing, the baseline tracking algorithm will work in the same direction as the temperature change and can cause the data to go below the button threshold even though the button is still pressed. Even at a steady state temperature, if the baseline tracking is not paused during a button press, then the data can creep below the threshold and turn off the digital output for an extended button press. For this reason, the max time of an expected button press can have an impact on the fastest baseline increment setting that can be used in the application.


    Knowing these factors, it is important to understand how the temperature change will effect the sensor design in your application. This combined with the expected button response will give you information on how fast the baseline increment needs to be for your application.

    For more information on the baseline tracking algorithm and the baseline increment settings, please see the following:

    Best Regards,

    Justin Beigel