SNOSCZ4A April   2015  – October 2024 FDC1004-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 I2C Interface Voltage Level
    7. 5.7 I2C Interface Timing
    8. 5.8 Typical Characteristics
  7. 6 Detailed Description
    1. 6.1 Overview
    2. 6.2 Functional Block Diagram
    3. 6.3 Feature Description
      1. 6.3.1 The Shield
      2. 6.3.2 The CAPDAC
      3. 6.3.3 Capacitive System Offset Calibration
      4. 6.3.4 Capacitive Gain Calibration
    4. 6.4 Device Functional Modes
      1. 6.4.1 Single Ended Measurement
      2. 6.4.2 Differential Measurement
    5. 6.5 Programming
      1. 6.5.1 Serial Bus Address
      2. 6.5.2 Read/Write Operations
      3. 6.5.3 Device Usage
        1. 6.5.3.1 Measurement Configuration
        2. 6.5.3.2 Triggering Measurements
        3. 6.5.3.3 Wait for Measurement Completion
        4. 6.5.3.4 Read of Measurement Result
    6. 6.6 Register Maps
      1. 6.6.1 Registers
        1. 6.6.1.1 Capacitive Measurement Registers
      2. 6.6.2 Measurement Registers
      3. 6.6.3 Measurement Configuration Registers
      4. 6.6.4 FDC Configuration Register
      5. 6.6.5 Offset Calibration Registers
      6. 6.6.6 Gain Calibration Registers
      7. 6.6.7 Manufacturer ID Register
      8. 6.6.8 Device ID Register
  8. 7 Applications and Implementation
    1. 7.1 Application Information
      1. 7.1.1 Liquid Level Sensor
    2. 7.2 Typical Application
      1. 7.2.1 Design Requirements
      2. 7.2.2 Detailed Design Procedure
      3. 7.2.3 Application Curve
    3. 7.3 Best Design Practices
    4. 7.4 Initialization Set Up
    5. 7.5 Power Supply Recommendations
    6. 7.6 Layout
      1. 7.6.1 Layout Guidelines
      2. 7.6.2 Layout Example
  9. 8 Device and Documentation Support
    1. 8.1 Documentation Support
      1. 8.1.1 Related Documentation
    2. 8.2 Receiving Notification of Documentation Updates
    3. 8.3 Support Resources
    4. 8.4 Trademarks
    5. 8.5 Electrostatic Discharge Caution
    6. 8.6 Glossary
  10. 9 Revision History
  11. 10Mechanical, Packaging, and Orderable Information

Package Options

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

7.1.1 Liquid Level Sensor

The FDC1004-Q1 can be used to measure liquid level in non-conductive containers. Capacitive sensors can be attached to the outside of the container or be located remotely from the container, allowing for contact-less measurements. The working principle is based on a ratiometric measurement; Figure 7-1 shows a possible system implementation which uses three electrodes. The Level electrode provides a capacitance value proportional to the liquid level. The Reference Environmental electrode and the Reference Liquid electrode are used as references. The Reference Liquid electrode accounts for the liquid dielectric constant and variation, while the Reference Environmental electrode is used to compensate for any other environmental variations that are not due to the liquid itself. Note that the Reference Environmental electrode and the Reference Liquid electrode are the same physical size (hREF).

For this application, single-ended measurements on the appropriate channels are appropriate, as the tank is grounded.

Use the following formula to determine the liquid level from the measured capacitances:

FDC1004-Q1

where

  • CRE is the capacitance of the Reference Environmental electrode,
  • CRL is the capacitance of the Reference Liquid electrode,
  • CLev is the current value of the capacitance measured at the Level electrode sensor,
  • CLev(0) is the capacitance of the Level electrode when the container is empty, and
  • hREF is the height in the desired units of the Container or Liquid Reference electrodes.

The ratio between the capacitance of the level and the reference electrodes allows simple calculation of the liquid level inside the container itself. Very high sensitivity values (that is, many LSB/mm) can be obtained due to the high resolution of the FDC1004-Q1, even when the sensors are located remotely from the container.

For more information on a robust liquid level sensing technique, refer to application note Capacitive Sensing: Out-of-Phase Liquid Level Technique application note and the (TIDA-00317 Capacitive-Based Liquid Level Sensing Sensor Reference Design).