SNOSCZ0A December   2014  – March 2018 LDC1312 , LDC1314

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
      2.      Measurement Precision vs. Target Distance
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin 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 Switching Characteristics - I2C
    7. 6.7 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 Multi-Channel and Single Channel Operation
      2. 7.3.2 Adjustable Conversion Time
      3. 7.3.3 Digital Signal Gain
      4. 7.3.4 Sensor Startup and Glitch Configuration
      5. 7.3.5 Reference Clock
      6. 7.3.6 Sensor Current Drive Control
      7. 7.3.7 Device Status Monitoring
    4. 7.4 Device Functional Modes
      1. 7.4.1 Startup Mode
      2. 7.4.2 Sleep Mode (Configuration Mode)
      3. 7.4.3 Normal (Conversion) Mode
      4. 7.4.4 Shutdown Mode
        1. 7.4.4.1 Reset
    5. 7.5 Programming
      1. 7.5.1 I2C Interface Specifications
      2. 7.5.2 Pulses on I2C
    6. 7.6 Register Maps
      1. 7.6.1  Register List
      2. 7.6.2  Address 0x00, DATA0
        1. Table 1. Address 0x00, DATA0 Field Descriptions
      3. 7.6.3  Address 0x02, DATA1
        1. Table 2. Address 0x02, DATA1 Field Descriptions
      4. 7.6.4  Address 0x04, DATA2 (LDC1314 only)
        1. Table 3. Address 0x04, DATA2 Field Descriptions
      5. 7.6.5  Address 0x06, DATA3 (LDC1314 only)
        1. Table 4. Address 0x06, DATA3 Field Descriptions
      6. 7.6.6  Address 0x08, RCOUNT0
        1. Table 5. Address 0x08, RCOUNT0 Field Descriptions
      7. 7.6.7  Address 0x09, RCOUNT1
        1. Table 6. Address 0x09, RCOUNT1 Field Descriptions
      8. 7.6.8  Address 0x0A, RCOUNT2 (LDC1314 only)
        1. Table 7. Address 0x0A, RCOUNT2 Field Descriptions
      9. 7.6.9  Address 0x0B, RCOUNT3 (LDC1314 only)
        1. Table 8. Address 0x0B, RCOUNT3 Field Descriptions
      10. 7.6.10 Address 0x0C, OFFSET0
        1. Table 9. OFFSET0 Field Descriptions
      11. 7.6.11 Address 0x0D, OFFSET1
        1. Table 10. Address 0x0D, OFFSET1 Field Descriptions
      12. 7.6.12 Address 0x0E, OFFSET2 (LDC1314 only)
        1. Table 11. Address 0x0E, OFFSET2 Field Descriptions
      13. 7.6.13 Address 0x0F, OFFSET3 (LDC1314 only)
        1. Table 12. Address 0x0F, OFFSET3 Field Descriptions
      14. 7.6.14 Address 0x10, SETTLECOUNT0
        1. Table 13. Address 0x10, SETTLECOUNT0 Field Descriptions
      15. 7.6.15 Address 0x11, SETTLECOUNT1
        1. Table 14. Address 0x11, SETTLECOUNT1 Field Descriptions
      16. 7.6.16 Address 0x12, SETTLECOUNT2 (LDC1314 only)
        1. Table 15. Address 0x12, SETTLECOUNT2 Field Descriptions
      17. 7.6.17 Address 0x13, SETTLECOUNT3 (LDC1314 only)
        1. Table 16. Address 0x13, SETTLECOUNT3 Field Descriptions
      18. 7.6.18 Address 0x14, CLOCK_DIVIDERS0
        1. Table 17. Address 0x14, CLOCK_DIVIDERS0 Field Descriptions
      19. 7.6.19 Address 0x15, CLOCK_DIVIDERS1
        1. Table 18. Address 0x15, CLOCK_DIVIDERS1 Field Descriptions
      20. 7.6.20 Address 0x16, CLOCK_DIVIDERS2 (LDC1314 only)
        1. Table 19. Address 0x16, CLOCK_DIVIDERS2 Field Descriptions
      21. 7.6.21 Address 0x17, CLOCK_DIVIDERS3 (LDC1314 only)
        1. Table 20. Address 0x17, CLOCK_DIVIDERS3
      22. 7.6.22 Address 0x18, STATUS
        1. Table 21. Address 0x18, STATUS Field Descriptions
      23. 7.6.23 Address 0x19, ERROR_CONFIG
        1. Table 22. Address 0x19, ERROR_CONFIG
      24. 7.6.24 Address 0x1A, CONFIG
        1. Table 23. Address 0x1A, CONFIG Field Descriptions
      25. 7.6.25 Address 0x1B, MUX_CONFIG
        1. Table 24. Address 0x1B, MUX_CONFIG Field Descriptions
      26. 7.6.26 Address 0x1C, RESET_DEV
        1. Table 25. Address 0x1C, RESET_DEV Field Descriptions
      27. 7.6.27 Address 0x1E, DRIVE_CURRENT0
        1. Table 26. Address 0x1E, DRIVE_CURRENT0 Field Descriptions
      28. 7.6.28 Address 0x1F, DRIVE_CURRENT1
        1. Table 27. Address 0x1F, DRIVE_CURRENT1 Field Descriptions
      29. 7.6.29 Address 0x20, DRIVE_CURRENT2 (LDC1314 only)
        1. Table 28. Address 0x20, DRIVE_CURRENT2 Field Descriptions
      30. 7.6.30 Address 0x21, DRIVE_CURRENT3 (LDC1314 only)
        1. Table 29. DRIVE_CURRENT3 Field Descriptions
      31. 7.6.31 Address 0x7E, MANUFACTURER_ID
        1. Table 30. Address 0x7E, MANUFACTURER_ID Field Descriptions
      32. 7.6.32 Address 0x7F, DEVICE_ID
        1. Table 31. Address 0x7F, DEVICE_ID Field Descriptions
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Conductive Objects in a Time-Varying EM Field
      2. 8.1.2 L-C Resonators
      3. 8.1.3 Multi-Channel and Single Channel Operation
        1. 8.1.3.1 Data Offset
        2. 8.1.3.2 Digital Signal Gain
      4. 8.1.4 Sensor Conversion Time
        1. 8.1.4.1 Settling Time
        2. 8.1.4.2 Sensor Activation
      5. 8.1.5 Sensor Current Drive Configuration
        1. 8.1.5.1 Inactive Channel Sensor Connections
        2. 8.1.5.2 Automatic IDRIVE Setting with RP_OVERRIDE_EN
        3. 8.1.5.3 Determining Sensor IDRIVE for an Unknown Sensor RP Using an Oscilloscope
        4. 8.1.5.4 Sensor Auto-Calibration Mode
        5. 8.1.5.5 Channel 0 High Current Drive
      6. 8.1.6 Clocking Architecture
      7. 8.1.7 Input Deglitch Filter
      8. 8.1.8 Device Status Registers
      9. 8.1.9 Multi-Channel Data Readback
    2. 8.2 Typical Application
      1. 8.2.1 System Sensing Functionality
      2. 8.2.2 Example Application
      3. 8.2.3 Design Requirements
      4. 8.2.4 Detailed Design Procedure
      5. 8.2.5 Recommended Initial Register Configuration Values
      6. 8.2.6 Application Curves
      7. 8.2.7 Inductor Self-Resonant Frequency
  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 Device Support
      1. 11.1.1 Development Support
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

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

8.1.5 Sensor Current Drive Configuration

The registers listed in Table 38 are used to control the sensor drive current so that the sensor signal amplitude is within the optimum range of 1.2 VP to 1.8 VP (sensor amplitudes outside this optimum range can be reported in the status register - refer to Device Status Registers ). The device can still convert with sensor amplitudes lower than 0.6 VP, however the conversion noise will increase with lower sensor amplitudes. Below 0.6 VP the sensor oscillations may not be stable or may completely stop and the LDC will stop converting. If the current drive results in the oscillation amplitude greater than 1.8 V, the internal ESD clamping circuit will become active. This may cause the sensor frequency to shift so that the output values no longer represent a valid system state. Figure 53 shows the block diagram of the sensor driver. Each channel has an independent setting for the IDRIVE current used to set the sensor oscillation amplitude.

LDC1312 LDC1314 ldc1312-sensor-drive-snoscz0.gifFigure 53. LDC1314 Sensor Driver Block Diagram

Table 38. Current Drive Control Registers

CHANNEL(1) REGISTER FIELD [ BIT(S) ] VALUE
All CONFIG, addr 0x1A SENSOR_ACTIVATE_SEL [11] Sets current drive for sensor activation. Recommended value is b0 (Full Current mode).
RP_OVERRIDE_EN [12] Set to b1 for normal operation (RP Override enabled)
AUTO_AMP_DIS [10] Disables Automatic amplitude correction. Set to b1 for normal operation (disabled)
0 CONFIG, addr 0x1A HIGH_CURRENT_DRV [6] b0 = normal current drive (1.5 mA)
b1 = Increased current drive (> 1.5 mA) for Ch 0 in single channel mode only. Cannot be used in multi-channel mode.
0 DRIVE_CURRENT0, addr 0x1E IDRIVE0 [15:11] Drive current used during the settling and conversion time for Ch. 0 (auto-amplitude correction must be disabled and RP over ride=1 )
INIT_IDRIVE0 [10:6] Initial drive current stored during auto-calibration. Not used for normal operation.
1 DRIVE_CURRENT1, addr 0x1F IDRIVE1 [15:11] Drive current used during the settling and conversion time for Ch. 1 (auto-amplitude correction must be disabled and RP over ride=1 )
INIT_IDRIVE1 [10:6] Initial drive current stored during auto-calibration. Not used for normal operation.
2 DRIVE_CURRENT2, addr 0x20 IDRIVE2 [15:11] Drive current used during the settling and conversion time for Ch. 2 (auto-amplitude correction must be disabled and RP over ride=1 )
INIT_IDRIVE2 [10:6] Initial drive current stored during auto-calibration. Not used for normal operation.
3 DRIVE_CURRENT3, addr 0x21 IDRIVE3 [15:11] Drive current used during the settling and conversion time for Ch. 3 (auto-amplitude correction must be disabled and RP over ride=1 )
INIT_IDRIVE3 [10:6] Initial drive current stored during auto-calibration. Not used for normal operation.
(1) Channels 2 and 3 are available for LDC1314 only.

If the RP value of the sensor attached to Channel x is known, Table 39 can be used to select the 5-bit value to be programmed into the IDRIVEx field for the channel. If the measured RP (at maximum spacing between the sensor and the target) falls between two of the table values, use the current drive value associated with the lower RP from the table. All channels that use an identical sensor/target configuration can use the same IDRIVEx value. The appropriate sensor drive current can be calculated with:

Equation 12. IDRIVE = πVP ÷ 4RP

Table 39. Optimum Sensor RP Ranges for Sensor IDRIVEx Setting.

IDRIVEx Register Field Value Nominal Sensor Current (µA) Minimum Sensor RP (kΩ) Maximum Sensor RP (kΩ)
0 b00000 16 60.0 90.0
1 b00001 18 51.8 77.6
2 b00010 20 44.6 66.9
3 b00011 23 38.4 57.6
4 b00100 28 33.7 49.7
5 b00101 32 29.5 42.8
6 b00110 40 23.6 36.9
7 b00111 46 20.5 31.8
8 b01000 52 18.1 27.4
9 b01001 59 16.1 23.6
10 b01010 72 13.1 20.4
11 b01011 82 11.5 17.6
12 b01100 95 9.92 15.1
13 b01101 110 8.57 13.0
14 b01110 127 7.42 11.2
15 b01111 146 6.46 9.69
16 b10000 169 5.58 8.35
17 b10001 195 4.83 7.20
18 b10010 212 4.45 6.21
19 b10011 244 3.86 5.35
20 b10100 297 3.17 4.61
21 b10101 342 2.76 3.97
22 b10110 424 2.22 3.42
23 b10111 489 1.93 2.95
24 b11000 551 1.71 2.54
25 b11001 635 1.48 2.19
26 b11010 763 1.24 1.89
27 b11011 880 1.07 1.63
28 b11100 1017 0.93 1.40
29 b11101 1173 0.80 1.21
30 b11110 1355 0.70 1.05
31 b11111 1563 0.60 0.90

Sensors with RP greater than 90 kΩ can be driven by placing a 100 kΩ resistor in parallel with the sensor inductor to reduce the effective RP.

Sensors which have a wide range of RP may require more than one current drive setting across the range of operation - the current would need to be dynamically set based on the target position. Note that some high-resolution applications will experience an output code offset when the current drive is changed. Another approach for systems which have a wide range of RP is to place a discrete resistor in parallel with the inductor to limit the range of RP variation in the system. This will also reduce the sensor Q, and so may not be feasible for some implementations.