SNOSDC7B December   2021  – December 2021 LDC3114-Q1

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Digital Interface
    7. 6.7 I2C Interface
    8. 6.8 Timing Diagram
    9. 6.9 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Multimode Operation
      2. 7.3.2 Multichannel and Single-Channel Operation
      3. 7.3.3 Raw Data Output
      4. 7.3.4 Button Output Interfaces
      5. 7.3.5 Programmable Button Sensitivity
      6. 7.3.6 Baseline Tracking
      7. 7.3.7 Integrated Button Algorithms
      8. 7.3.8 I2C Interface
        1. 7.3.8.1 I2C Interface Specifications
        2. 7.3.8.2 I2C Bus Control
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Power Mode
      2. 7.4.2 Low Power Mode
      3. 7.4.3 Configuration Mode
    5. 7.5 Register Maps
      1. 7.5.1 LDC3114 Registers
      2. 7.5.2 Gain Table for Registers GAIN0, GAIN1, GAIN2, and GAIN3
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1  Theory of Operation
      2. 8.1.2  Designing Sensor Parameters
      3. 8.1.3  Setting COM Pin Capacitor
      4. 8.1.4  Defining Power-On Timing
      5. 8.1.5  Configuring Button or Raw Data Scan Rate
      6. 8.1.6  Programming Button or Raw Data Sampling Window
      7. 8.1.7  Scaling Frequency Counter Output
      8. 8.1.8  Setting Button Triggering Threshold
      9. 8.1.9  Tracking Baseline
      10. 8.1.10 Mitigating False Button Detections
        1. 8.1.10.1 Eliminating Common-Mode Change (Anti-Common)
        2. 8.1.10.2 Resolving Simultaneous Button Presses (Max-Win)
        3. 8.1.10.3 Overcoming Case Twisting (Anti-Twist)
        4. 8.1.10.4 Mitigating Metal Deformation (Anti-Deform)
      11. 8.1.11 Reporting Interrupts for Button Presses, Raw Data Ready and Error Conditions
      12. 8.1.12 Estimating Supply Current
    2. 8.2 Typical Application
      1. 8.2.1 Touch Button Design
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
    1. 12.1 Tape and Reel Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.1.9 Tracking Baseline

The LDC3114-Q1 automatically tracks slow changes in the baseline signal and compensates for environmental drifts and variations. The baseline tracking is only applicable for the button algorithm mode and not for raw data access mode. See Section 7.3.1 for details. In Normal Power Mode, use Equation 11 to determine the effective baseline increment per scan cycle (BINCNP):

Equation 11. GUID-19841696-EEE4-48B6-9535-E06770BE7601-low.gif

where:

  • NPBI is the Normal Power Baseline Increment index that can be configured in Register NP_BASE_INC (Address 0x15)

In Low Power Mode, use Equation 12 to determine the effective baseline increment per scan cycle (BINCLP):

Equation 12. GUID-DF1A1200-28B7-49DA-BA8C-E47B9AF9597E-low.gif

where:

  • LPBI the Low Power Baseline Increment index that can be configured in Register LP_BASE_INC (Address 0x13)

As a result of baseline tracking, a button press with a constant force only lasts for a finite amount of time. Equation 13 defines the duration of a button press (DATAn > ThresholdON).

Equation 13. GUID-4E44F5A8-0DE4-4D8E-8786-3A21883D2ACF-low.gif

where:

  • Duration of Button Press is the number of scan cycles that the channel is asserted
  • DATAn is the button signal at the beginning of a press
  • BINC is the baseline increment per scan cycle
GUID-33208DC9-D561-47B5-89D9-070EC5F3E775-low.gifFigure 8-9 Baseline Tracking in the Presence of a Button Press

The baseline tracking for a particular channel can be paused when the channel output is asserted. This is achieved by setting the corresponding BTPAUSE bit in Register BTPAUSE_MAXWIN (Address 0x16) to b1.

If DATAn is negative, the tracking speed will be scaled by the fast tracking factor as specified in Registers FTF0 (Address 0x25) , FTF1_2 (Address 0x28), or FTF3 (Address 0x2B). Table 8-2 shows the scaling factors for various FTFn settings.

Equation 14. BINC (DATAn < 0) = Fast_Tracking_Factor_n × BINC (DATAn > 0)
Table 8-2 Fast Tracking Factor Settings
FTFn SettingFast Tracking Factor
b001
b014
b108
b1116
Note: When the continuous sampling rate using NPCS bit is set, the baseline tracking increment is a fixed value.