SNAS662 July   2015 TDC1011

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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 Timing Requirements
    7. 6.7 Switching Characteristics
    8. 6.8 Typical Characteristics
  7. Parameter Measurement Information
  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 Function Description
      1. 8.4.1 Time-of-Flight Measurement Mode
        1. 8.4.1.1 Liquid Level or Fluid Identification
      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 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
      1. 8.6.1 TDC1011 Registers
        1. 8.6.1.1  CONFIG_0 Register (address = 0h) [reset = 45h]
        2. 8.6.1.2  CONFIG_1 Register (address = 1h) [reset = 40h]
        3. 8.6.1.3  CONFIG_2 Register (address = 2h) [reset = 0h]
        4. 8.6.1.4  CONFIG_3 Register (address 3h) [reset = 3h]
        5. 8.6.1.5  CONFIG_4 Register (address = 4h) [reset = 1Fh]
        6. 8.6.1.6  TOF_1 Register (address = 5h) [reset = 0h]
        7. 8.6.1.7  TOF_0 Register (address = 6h) [reset = 0h]
        8. 8.6.1.8  ERROR_FLAGS Register (address = 7h) [reset = 0h]
        9. 8.6.1.9  TIMEOUT Register (address = 8h) [reset = 19h]
        10. 8.6.1.10 CLOCK_RATE Register (address = 9h) [reset = 0h]
  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
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Device Support
      1. 12.1.1 Third-Party Products Disclaimer
      2. 12.1.2 Development Support
    2. 12.2 Community Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

9.1 Application Information

The TDC1011 is an analog front-end for ultrasonic sensing applications. The device is typically used for the driving and sensing of ultrasonic transducers to perform accurate time-of-flight measurements. Ultrasonic time-of-flight sensing allows for fluid level, fluid identification or concentration measurements.

9.2 Typical Applications

9.2.1 Level and Fluid Identification Measurements

TDC1011 app_lvl_concent_NAS648.gifFigure 51. Level or Concentration Measurement Application Diagram

9.2.1.1 Design Requirements

Table 14. Design Parameters

DESIGN PARAMETER EXAMPLE VALUE
Fluid Level
Range 2 – 10 cm
Fluid Identification
Accuracy 0.5% concentration variation
Distance 5.08 cm

9.2.1.2 Detailed Design Procedure

9.2.1.2.1 Level Measurements

For level sensing applications, the total time-of-flight (TOF) of the sound wave in the fluid is measured. The pulses transmitted by a bottom mounted transducer travel through the fluid, to the surface of the fluid. The discontinuity between the fluid and air generates a reflected wave which returns back to the bottom mounted transducer.

At the beginning of a measurement cycle, the transducer is connected to a transmit channel of the AFE, and the transmit burst excites the transducer to generate an ultrasound wave. Synchronous to the TX burst, a START pulse is generated by the TDC1011 to indicate the start of a measurement. After the transmission is completed, and depending on the device configuration, the transducer is connected to a receive channel of the AFE.

When a valid echo is received, the TDC1011 generates a STOP pulse. Generation of multiple STOP pulses is possible through register configuration of the device. The START and STOP signal times are compared to determine the TOF.

The level of the fluid can be determined using the following equation:

Equation 6. TDC1011 eq_lvl_d_NAS648.gif

where

  • d is the fluid level in meters (m)
  • TOF is the time-of-flight in seconds (s)
  • c is the speed of sound in the fluid in meters per second (m/s)
TDC1011 lvl_meter_pulses_NAS648.gifFigure 52. Relation Between Transmit and Receive Pulses in Level Measurements

Level measurements have 2 main criteria: resolution and range (maximum height). Resolution accuracies of 1-2 mm are achievable but are impractical due to any environmental disturbances, such as tank vibrations, creating millimeter level surface waves. Ranges of up to 1 m are measurable utilizing VDD level excitation pulses, but surface disturbances and signal loss over longer distances make the reliable echo reception an issue. Greater level measurement reception can be achieved by mechanical means (level guide tube) and/or electronic means (level shifting the TX pulses to greater voltages; see TIDA-00322).

9.2.1.2.2 Fluid Identification

The TDC1011 can be used to measure the time-of-flight for a known distance to calculate the speed of sound (cmedium) in the fluid. This application utilizes the same circuitry as the level example but a transducer in a side mounted configuration transmitting across the container or to a target at a known distance from the transducer.

The temperature can also be measured to compensate for the temperature variation of sound. With the known distance, TOF and temperature, the speed of sound in the fluid can be determined and the identity of the medium verified.

After measuring the time-of-flight for the fixed distance, the speed of sound can be calculated as follows:

Equation 7. TDC1011 eq_lvl_c_NAS648.gif

where

  • cmedium is the speed of sound in the fluid in meters per second (m/s)
  • d is the level in meters (m)
  • TOF is the time of flight in seconds (s)

The measurement process is identical to the level example above. The speed of sound can be used to uniquely identify a variety of fluids. In this example, the concentration of diesel exhaust fluid (DEF) is measured with a desired accuracy resolution of 0.5% of concentration variation. For most fluids, the speed of sound varies over temperature, so every application will be different. In this example, all samples were all at ambient temperature of 23°C.

9.2.1.3 Application Curves

The data used in the following level and fluid identification graphs was collected using an ultrasonic test cell. The test cell is an acrylic plastic container with width of 2.54 cm and ultrasonic transducers attached to the outside using cyanoacrylate glue. The transducers in this experiment were STEMiNC 1MHz piezo electric ceramic discs (SMD10T2R111). Equivalent transducers with the following characteristics could be used:

  • Piezo material: SM111
  • Dimensions: 10mm diameter x 2mm thickness
  • Resonant frequency: 1050 kHz (thickness mode)

TDC1011 D015_SNAS648.gif

Fluid Height in Tank Time-of-Flight (µs)
Full (10 cm) 145
Full – 1 (9 cm) 131
Full – 2 (8 cm) 118
3 cm 50
2 cm 35
Figure 53. Time-of-Flight for Fluid Height in Tank
TDC1011 D019_SNAS648.gif

Fluid Speed of sound (m/s)
Distilled water 1481.87
Tap water 1483.13
Figure 55. Speed of Sound in Distilled Water and Tap Water
TDC1011 D018_SNAS648.gif

Fluid Speed of sound (m/s)
Distilled water 1481.87
Tap water 1483.13
DEF 10.0% 1530.49
DEF 20.0% 1576.42
DEF 30.0% 1620.00
DEF 31.5% 1627.37
DEF 32.0% 1629.15
DEF 32.5% 1630.00
Figure 54. Speed of Sound for Various Fluids and Diesel Exhaust Fluid (DEF) Concentration
TDC1011 D020_SNAS648.gif

Fluid Speed of sound (m/s)
DEF 30.0% 1620.00
DEF 31.5% 1627.37
DEF 32.0% 1629.15
DEF 32.5% 1630.00
Figure 56. Speed of Sound of Various Diesel Exhaust Fluid (DEF) Concentrations