SNOA954D November   2019  – June 2021 LDC0851 , LDC1001 , LDC1001-Q1 , LDC1041 , LDC1051 , LDC1101 , LDC1312 , LDC1312-Q1 , LDC1314 , LDC1314-Q1 , LDC1612 , LDC1612-Q1 , LDC1614 , LDC1614-Q1 , LDC2112 , LDC2114 , LDC3114 , LDC3114-Q1

 

  1.   Trademarks
  2. 1LDC Applications
    1. 1.1 Axial Sensing
      1. 1.1.1 Buttons and Keypads
    2. 1.2 Event Counting
    3. 1.3 Other Types of Sensing
  3. 2Inductive Sensing Theory of Operation
  4. 3LDC Device Feature Overview
    1. 3.1 Sample Rate
    2. 3.2 Sensor L Measurement and Reference Frequency
    3. 3.3 Sensor RP Measurement
    4. 3.4 Sensor RP (Current) Drive Capability
    5. 3.5 Switch Output Functionality
    6. 3.6 Sensor Frequency Range
    7. 3.7 Multi-Channel Sensing
    8. 3.8 Power Management
    9. 3.9 Internal Algorithms
  5. 4Device Families
    1. 4.1 Inductive Touch Devices
      1. 4.1.1 Inductive Touch LDC Recommended Applications
    2. 4.2 Multichannel LDC Devices
      1. 4.2.1 Multi-Channel LDC Recommended Applications
      2. 4.2.2 LDC1101
        1. 4.2.2.1 LDC1101 Recommended Applications
      3. 4.2.3 LDC0851
        1. 4.2.3.1 Recommended Applications
  6. 5Summary
  7. 6Revision History

3.2 Sensor L Measurement and Reference Frequency

LDC devices determine the sensor inductance by measuring the sensor frequency with the relationship in Equation 1. A reference frequency of some source is needed.

Some LDC devices, such as the LDC1314, provide the choice of using either an internal oscillator or an external reference oscillator, while others such as the LDC1101 require an external oscillator. For a given sample frequency, devices that are able to use a higher reference frequency can provide higher measurement resolution.

If the LDC requires an external oscillator, it should be a square wave with low jitter (<100 psRMS), frequency stable, and have a 50% duty cycle.