JAJU680A January   2019  – July 2022

 

  1.   概要
  2.   Resources
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Flow Measurement
      2. 2.2.2 ToF Measurement
        1. 2.2.2.1 ADC-Based Acquisition Process
        2. 2.2.2.2 Ultrasonic Sensing Flow-Metering Library
      3. 2.2.3 Low-Power Design
        1. 2.2.3.1 Energy-Efficient Software
        2. 2.2.3.2 Optimized Hardware Design
        3. 2.2.3.3 Efficient Use of FRAM
        4. 2.2.3.4 The LEA Advantage
    3. 2.3 Highlighted Products
      1. 2.3.1 MSP430FR6043
      2. 2.3.2 OPA836 and OPA838
      3. 2.3.3 TS5A9411
    4. 2.4 System Design Theory
      1. 2.4.1 Signal Processing for ToF
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
        1. 3.1.1.1 EVM430-FR6043
      2. 3.1.2 Software
        1. 3.1.2.1 MSP Driver Library (MSP DriverLib)
        2. 3.1.2.2 Ultrasonic Sensing Flow Metering Library
        3. 3.1.2.3 Application
          1. 3.1.2.3.1 Application Customization
          2. 3.1.2.3.2 LCD Stand-Alone Mode
        4. 3.1.2.4 USS Design Center (PC GUI)
      3. 3.1.3 Transducer and Meter
        1. 3.1.3.1 Frequency Characterization of Transducer and Meter
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
        1. 3.2.1.1 Connecting Hardware
        2. 3.2.1.2 Building and Loading Software
          1. 3.2.1.2.1 Using Code Composer Studio IDE
          2. 3.2.1.2.2 Using IAR Embedded Workbench IDE
        3. 3.2.1.3 Executing Application
        4. 3.2.1.4 Configure Device and Observe Results Using GUI
        5. 3.2.1.5 Customization and Optimization
      2. 3.2.2 Test Results
        1. 3.2.2.1 Single-Shot Standard Deviation
        2. 3.2.2.2 Zero-Flow Drift
        3. 3.2.2.3 Absolute Time of Flight Measurements
        4. 3.2.2.4 Variability in Zero Flow Drift Across Transducers
        5. 3.2.2.5 Flow Measurements
        6. 3.2.2.6 Average Current Consumption
        7. 3.2.2.7 Memory Footprint
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 Bill of Materials
      3. 4.1.3 PCB Layout Recommendations
        1. 4.1.3.1 Layout Prints
      4. 4.1.4 Altium Project
      5. 4.1.5 Gerber Files
      6. 4.1.6 Assembly Drawings
    2. 4.2 Software Files
    3. 4.3 Related Documentation
    4. 4.4 Terminology
    5. 4.5 Trademarks
    6. 4.6 サポート・リソース
  10. 5About the Authors
  11. 6Revision History

3.2.2.6 Average Current Consumption

The average current consumption is an important consideration for power-restricted systems, such as battery-operated gas-flow meters.

The current consumption of the device depends on several different parameters, which can be configured using the MSP430 Ultrasonic Design Center GUI. These parameters include the transducer frequency, number of pulses, gap between UPS and DNS, measurement rate (DNS-UPS gap), signal sampling frequency, and capture duration.

The optimal configuration of these parameters depends on the meter and a trade-off between performance and power consumption exists (see Figure 4-19).

GUID-DF570605-C9B1-45F7-9FF8-E14B6F12812B-low.gifFigure 4-19 Profile of Current Consumption During Duration of Measurement

The current profile in Figure 4-19 is based on a gas meter pipe and the MSP430FR6043 MCU, with parameters configured as listed in Table 4-5. For brevity, it does not include configuration parameters that have no impact on current consumption.

Table 4-5 Configuration for Current Measurements
Transmit Frequency (kHz)170 kHz to 240 kHz
Gap Between Pulse Start and ADC Capture (µs)200 µs
Number of Pulses24
UPS and DNS Gap (µs)8000 (for 8 ms)
UPS0 to UPS1 Gap (ms)1000 ms
Signal Sampling Frequency (kHz)1000 kHz
ADC Oversampling Rate80
Delta ToF Offset (ps)0
Absolute ToF Additional Delay (ns)0
Algorithm Option2
Envelope Crossing Threshold50
Capture Duration (µs)250 µs
Start PPG Count (ns)400000 (for 400 µs)
Turn on ADC Count (ns)10000 (for 10 µs)
Start PGA and IN Bias Count (ns)200000 (for 200 µs)
USS XTAL Settling Count (µs)120 µs
External Amplifier Count (ns)10000
User Param #8384

As shown in Figure 4-19, the instantaneous current consumption varies depending on the state of the software. Table 4-6 describes the states.

Table 4-6 States in Each Measurement for Current Consumption
StateDurationAverage Current ConsumptionDescription Of State
CLK Init188 µs809 µAInitialization of USSXT. The USS module is off.
USS Init (UPS)129 µs941 µAThe USS module is on, and registers of all submodules are initialized.
Upstream Pulse1.05 ms4.69 mAUpstream pulse firing and signal capture
Upstream/Downstream Gap7.82 ms1.73 µAGap between UPS and DNS. The CPU is in LPM3.
USS Init (DNS)283 µs939 µAPrior to DNS firing, the USS module is on, and registers of all submodules are initialized.
Downstream Pulse1.05 ms4.83 mADNS pulse firing and signal capture
Data Processing4.05 µs1.62 mADToF, AbsToF, and VFR computation. The USS module is off.
Sleep985 ms2.12 µA (1.093 µA)Gap between the end of a measurement and start of the next measurement. The CPU is in LPM3. The USS module is off.