SNOSDD0 December   2021 LDC3114

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

Package Options

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

7.3.3 Raw Data Output

Raw data mode is enabled by setting BTN_ALG_EN=0x0 field in Register INTPOL Address 0x11. Figure 7-2 shows that this operation will extract data directly from the output of the inductance-to-digital converter.

The data is read from the I2C interface of the LDC3114. The DATA_RDY field in Register OUT (Address 0x01) indicates when new data is available for reading. In the raw data mode, the INTB pin also assserted when new data is available and can be used by the MCU as an interrupt. The raw data can be extracted by reading, the output RAW_DATAn_x registers (n = 0, 1, 2, or 3, for each channel, x= 1, 2, or 3 splitting 24-bit data over 3 8-bit register fields). Equation 1 shows the relationship between 24-bit data and the sensor frequency.

Equation 1. GUID-20200927-CA0I-J5NX-JVDJ-WF6BBCWFPJ1H-low.gif

where:

  • fsensor is the instantaneous frequency of the inductive sensor
  • fREF_CLK is the internal reference clock frequency as specified in Section 6.5
  • raw_data is the decimal representation of 24-bit binary data read from the RAW_DATAn_x for a particular channel
  • W calculated in Equation 2 (see Section 8.1.6 for details):
    Equation 2. GUID-20200927-CA0I-SPGG-RZST-X66VZTDFFRPQ-low.gif