SNOA993A June   2018  – July 2021 LDC2112 , LDC2114 , LDC3114 , LDC3114-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Scan Rate and Sampling Interval
    1. 2.1 Low Power Mode and Normal Power Mode
    2. 2.2 Button Sequencing and Error Handling
  4. 3Data Polarity and Timeout
    1. 3.1 Button Timeout
  5. 4Internal Algorithms Overview
  6. 5Baseline Tracking
    1. 5.1 Baseline Increment
    2. 5.2 Baseline Tracking Reset
    3. 5.3 Button Actuation Time
    4. 5.4 BTPAUSE
    5. 5.5 Fast Tracking Factor
  7. 6Gain, Hysteresis, and Threshold
    1. 6.1 Threshold and Hysteresis
  8. 7Multi-Button Algorithms
    1. 7.1 Max Win
    2. 7.2 Anti-Common Mode
    3. 7.3 Anti-Twist Factor
    4. 7.4 Anti-Deform Factor
  9. 8Summary
  10. 9Revision History

4 Internal Algorithms Overview

The LDC211x and LDC3114 devices take the output measurements for each channel and apply a sequence of several algorithms to the conversion results. Some of the algorithms are optional, and some can be configured per-channel. Table 4-1 below lists the internal algorithms and the configuration options applicable for each algorithm.

Table 4-1 LDC211x and LDC3114 Internal Algorithms
AlgorithmAlways Applied or Optional?ConfigurationPer ChannelFunctionality
Data PolarityAlwaysDPOLxYSelect Inductive or Capacitive sensing operation
Baseline TrackingAlwaysNPBI/LPBINCompensates for environmental shifts in inductance and capacitance.
Fast TrackingOptionalFTFYProvides faster recovery for negative swings in output code values.
GainAlwaysGAINxYAdjusts sensitivity of channel. Scales between 1x and 232x in 64 settings; average step delta is 9%.
Threshold CompareAlwaysN/ANCentered at 128. Effectively adjusted by use of GAINx.
HysteresisAlwaysHYSTNSets button actuation or deactivation thresholds. Centered at fixed Threshold Compare level of 128. Adjustable from 0 to 60 in steps of 4.
Baseline Tracking PauseOptionalBTPAUSExYDisables Baseline Tracking when OUTx value exceeds THRESHOLD+HYSTERSIS.

Baseline Tracking is disabled in raw data access mode of LDC3114.

Max WinOptionalMAXWINxYCompares OUTx across selected channels and deasserts OUTx signal for all but the highest value channel.
Anti-CommonOptionalANTICOMxYSuppress common-mode signal present on multiple channels which are due to mechanical cross-talk.
Anti-DeformOptionalANTIDFORMxYCompensate the baseline tracking for non-ideal recovery from mechanical stresses.
Anti-TwistOptionalANTITWISTNSuppress inverse signals present on multiple channels which are due to mechanical cross-talk.

The various algorithms are applied in the sequence shown in Figure 4-1. For algorithms which are optional, if the algorithm is not enabled, then the channel data is not modified in by block.

GUID-6F9AA2AB-58B8-48C3-B6CE-83EA7FA25703-low.gifFigure 4-1 Algorithm Sequence