SNAS648C October   2014  – February 2023 TDC1000

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 (1)
    5. 6.5 Electrical Characteristics
    6. 6.6 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. 7 Parameter Measurement Information
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Transmitter Signal Path
      2. 8.3.2 Receiver Signal Path
      3. 8.3.3 Low Noise Amplifier (LNA)
      4. 8.3.4 Programmable Gain Amplifier (PGA)
      5. 8.3.5 Receiver Filters
      6. 8.3.6 Comparators for STOP Pulse Generation
        1. 8.3.6.1 Threshold Detector and DAC
        2. 8.3.6.2 Zero-Cross Detect Comparator
        3. 8.3.6.3 Event Manager
      7. 8.3.7 Common-Mode Buffer (VCOM)
      8. 8.3.8 Temperature Sensor
        1. 8.3.8.1 Temperature Measurement With Multiple RTDs
        2. 8.3.8.2 Temperature Measurement With a Single RTD
    4. 8.4 Device Functional Modes
      1. 8.4.1 Time-of-Flight Measurement Mode
        1. 8.4.1.1 Mode 0
        2. 8.4.1.2 Mode 1
        3. 8.4.1.3 Mode 2
      2. 8.4.2 State Machine
      3. 8.4.3 TRANSMIT Operation
        1. 8.4.3.1 Transmission Pulse Count
        2. 8.4.3.2 TX 180° Pulse Shift
        3. 8.4.3.3 Transmitter Damping
      4. 8.4.4 RECEIVE Operation
        1. 8.4.4.1 Single Echo Receive Mode
        2. 8.4.4.2 Multiple Echo Receive Mode
      5. 8.4.5 Timing
        1. 8.4.5.1 Timing Control and Frequency Scaling (CLKIN)
        2. 8.4.5.2 TX/RX Measurement Sequencing and Timing
      6. 8.4.6 Time-of-Flight (TOF) Control
        1. 8.4.6.1 Short TOF Measurement
        2. 8.4.6.2 Standard TOF Measurement
        3. 8.4.6.3 Standard TOF Measurement With Power Blanking
        4. 8.4.6.4 Common-Mode Reference Settling Time
        5. 8.4.6.5 TOF Measurement Interval
      7. 8.4.7 Averaging and Channel Selection
      8. 8.4.8 Error Reporting
    5. 8.5 Programming
      1. 8.5.1 Serial Peripheral Interface (SPI)
        1. 8.5.1.1 Chip Select Bar (CSB)
        2. 8.5.1.2 Serial Clock (SCLK)
        3. 8.5.1.3 Serial Data Input (SDI)
        4. 8.5.1.4 Serial Data Output (SDO)
    6. 8.6 Register Maps
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 Level and Fluid Identification Measurements
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Level Measurements
          2. 9.2.1.2.2 Fluid Identification
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Water Flow Metering
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Regulations and Accuracy
          2. 9.2.2.2.2 Transit-Time in Ultrasonic Flow Meters
          3. 9.2.2.2.3 ΔTOF Accuracy Requirement Calculation
          4. 9.2.2.2.4 Operation
        3. 9.2.2.3 Application Curves
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  10. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  11. 11Mechanical, Packaging, and Orderable Information

8.3.8 Temperature Sensor

Accurate measurements of flow, level, and concentration require compensation for the temperature dependency of the speed of sound in the medium. The TDC1000 provides two temperature sensor connections, allowing to measure up to two locations with RTDs, as shown in #SNAS6489220.

GUID-1463AA86-5C15-4006-8694-C5D59BC705AA-low.gifFigure 8-9 Temperature Sensor Measurement

The temperature sensor block supports PT1000 or PT500 sensors. The type of RTD used must be selected in the TEMP_RTD_SEL bit of the CONFIG_3 register. The system requires a temperature-stable external reference resistor (RREF). If the RTD type is PT500, then RREF should be 500 Ω. If the RTD type is PT1000, then RREF should be 1 kΩ. The reference resistor needs to have either a low temperature coefficient or be calibrated for temperature shift.

The logic timing in a temperature measurement is controlled by the TEMP_CLK_DIV bit in the CONFIG_3 register. As shown in #SNAS6484652, the external clock can be divided by 8 or by the value resulting from the TX_FREQ_DIV field configuration in the CONFIG_0 register. TI recommends to operate the temperature measurement block at frequencies of 1 MHz or less.

GUID-163F509A-369B-41A4-9E4E-B95D7012D1B3-low.gifFigure 8-10 Timing Source for the Temperature Measurement