JAJSI72 November   2019 LDC1001

PRODUCTION DATA.  

  1. 特長
  2. アプリケーション
  3. 概要
    1.     軸方向距離検出アプリケーション
  4. 改訂履歴
  5. Pin Configuration and Functions
    1.     Pin Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Condition
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Inductive Sensing
      2. 7.3.2 Measuring RP With LDC1001
      3. 7.3.3 Measuring Inductance With LDC1001
    4. 7.4 Device Functional Modes
      1. 7.4.1 Power Modes
      2. 7.4.2 INTB Pin Modes
        1. 7.4.2.1 Comparator Mode
        2. 7.4.2.2 Wake-Up Mode
        3. 7.4.2.3 DRDY Mode
    5. 7.5 Programming
      1. 7.5.1 SPI Description
        1. 7.5.1.1 Extended SPI Transactions
    6. 7.6 Register Maps
      1. 7.6.1 Register Description
        1. 7.6.1.1  Revision ID (Address = 0x00)
        2. 7.6.1.2  RP_MAX (Address = 0x01)
        3. 7.6.1.3  RP_MIN (Address = 0x02)
        4. 7.6.1.4  Watchdog Timer Frequency (Address = 0x03)
        5. 7.6.1.5  LDC Configuration (Address = 0x04)
        6. 7.6.1.6  Clock Configuration (Address = 0x05)
        7. 7.6.1.7  Comparator Threshold High LSB (Address = 0x06)
        8. 7.6.1.8  Comparator Threshold High MSB (Address = 0x07)
        9. 7.6.1.9  Comparator Threshold Low LSB (Address = 0x08)
        10. 7.6.1.10 Comparator Threshold Low MSB (Address = 0x09)
        11. 7.6.1.11 INTB Pin Configuration (Address = 0x0A)
        12. 7.6.1.12 Power Configuration (Address = 0x0B)
        13. 7.6.1.13 Status (Address = 0x20)
        14. 7.6.1.14 Proximity Data LSB (Address = 0x21)
        15. 7.6.1.15 Proximity Data MSB (Address = 0x22)
        16. 7.6.1.16 Frequency Counter LSB (Address = 0x23)
        17. 7.6.1.17 Frequency Counter Mid-Byte (Address = 0x24)
        18. 7.6.1.18 Frequency Counter MSB (Address = 0x25)
  8. Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Calculation of RP_MIN and RP_MAX
        1. 8.1.1.1 RP_MAX
        2. 8.1.1.2 RP_MIN
      2. 8.1.2 Output Data Rate
      3. 8.1.3 Choosing Filter Capacitor (CFA and CFB Pins)
    2. 8.2 Typical Application
      1. 8.2.1 Axial Distance Sensing Using a PCB Sensor With LDC1001
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Sensor and Target
          2. 8.2.1.2.2 Calculating Sensor Capacitor
          3. 8.2.1.2.3 Choosing Filter Capacitor
          4. 8.2.1.2.4 Setting RP_MIN and RP_MAX
          5. 8.2.1.2.5 Calculating Minimum Sensor Frequency
        3. 8.2.1.3 Application Curve
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11デバイスおよびドキュメントのサポート
    1. 11.1 ドキュメントのサポート
      1. 11.1.1 関連資料
    2. 11.2 サポート・リソース
    3. 11.3 商標
    4. 11.4 静電気放電に関する注意事項
    5. 11.5 Glossary
  12. 12メカニカル、パッケージ、および注文情報

パッケージ・オプション

メカニカル・データ(パッケージ|ピン)
サーマルパッド・メカニカル・データ
発注情報

Inductive Sensing

An AC current flowing through an inductor will generate an AC magnetic field. If a conductive material, such as a metal target, is brought into the vicinity of the coil, this magnetic field will induce circulating currents (eddy currents) on the surface of the target. These eddy currents are a function of the distance, size, and composition of the target. The eddy currents then generate their own magnetic field, which opposes the original field generated by the coil. This mechanism is best compared to a transformer, where the coil is the primary core and the eddy current is the secondary core. The inductive coupling between both cores depends on distance and shape. Hence the resistance and inductance of the secondary core (eddy current), shows up as a distant dependent resistive and inductive component on the primary side (coil). Figure 5 and Figure 8 show a simplified circuit model.

LDC1001 inductor_modeled_resistor_snoscx2.gifFigure 5. Inductor With a Metal Target

Eddy currents generated on the surface of the target can be modeled as a transformer as shown in Figure 6. The coupling between the primary and secondary coils is a function of the distance and the characteristics of the conductor. In Figure 6, the inductance LS is the inductance of the coil, and RS is the parasitic series resistance of the coil. The inductance L(d), which is a function of sensor to target distance, d, is the coupled inductance of the metal target. Likewise, R(d) is the parasitic resistance of the eddy currents and is also a function of distance.

LDC1001 metal_target_eddy_currents_snoscx2.gifFigure 6. Metal Target Modeled as L and R With Circulating Eddy Currents

Generating an alternating magnetic field with just an inductor will consume a large amount of power. This power consumption can be reduced by adding a parallel capacitor, turning it into a resonator as shown in Figure 7. In this manner the power consumption is reduced to the eddy and inductor losses RS + R(d) only.

LDC1001 LC_tank_oscillator_snoscx2.gifFigure 7. LC Tank Connected to Oscillator

The LDC1001 doesn’t measure the series resistance directly; instead it measures the equivalent parallel resonance impedance RP (see Figure 8). This representation is equivalent to the one shown in Figure 8, where the parallel resonance impedance RP(d) is given by Equation 1:

Equation 1. LDC1001 eq01_snoscx2.gif
LDC1001 equivalent_res_parallel_LC_tank_snoscx2.gifFigure 8. Equivalent Resistance of RS in Parallel With LC Tank

Figure 9 shows the variation in RP as a function of distance for a 14-mm diameter PCB coil (refer to the sensor characteristics in Table 23). The target in this example is a section of a 2-mm thick stainless steel disk.

LDC1001 C002_snoscy1.pngFigure 9. Typical RP vs Distance With 14-mm PCB Coil