JAJU808 July   2021

 

  1.   概要
  2.   リソース
  3.   特長
  4.   アプリケーション
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1  System Control and Processing
      2. 2.2.2  Analog Front End
      3. 2.2.3  Input Voltage Monitoring: 5 V, 20 V, 40 V, and ±5 V
      4. 2.2.4  Bidirectional Current Sense: ±2 A
      5. 2.2.5  Unipolar Current Sense: 0.25 A to 1 A
      6. 2.2.6  TMP461-SP: Local and Remote Temperature Sensing
      7. 2.2.7  NTC Thermistor Temperature Sensing
      8. 2.2.8  Adjustable Voltage Source
      9. 2.2.9  Fixed Output Current Source
      10. 2.2.10 Adjustable 4-mA Current Source
      11. 2.2.11 Power Tree and Power Sequencing
    3. 2.3 Highlighted Products
      1. 2.3.1  MSP430FR5969-SP
      2. 2.3.2  ADC128S102QML-SP
      3. 2.3.3  DAC121S101QML-SP
      4. 2.3.4  LMP7704-SP
      5. 2.3.5  INA901-SP
      6. 2.3.6  LM4050QML-SP
      7. 2.3.7  LM158QML-SP
      8. 2.3.8  LM139QML-SP
      9. 2.3.9  TMP461-SP
      10. 2.3.10 TPS7A4501-SP
      11. 2.3.11 TPS7H2201-SP
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Required Hardware and Software
      1. 3.1.1 Hardware
      2. 3.1.2 Software
    2. 3.2 Test Setup
      1. 3.2.1 Voltage Monitor Test Setup
      2. 3.2.2 Current Monitor Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Voltage Measurement - Noise Floor Results
      2. 3.3.2 Voltage Measurement - Linearity Results
      3. 3.3.3 Current Measurement - Noise Floor Results
      4. 3.3.4 Current Measurement - Linearity Results
      5. 3.3.5 Analog Outputs
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Documentation Support
    3. 4.3 サポート・リソース
    4. 4.4 Trademarks
  10. 5About the Author

3.2.2 Current Monitor Test Setup

GUID-20210406-CA0I-GDHX-TFKH-1ZKLRQ9D4V28-low.gif Figure 3-3 Current Monitor Test Setup

To test the current monitoring circuits, a power supply and electronic load are required. The power supply provides a voltage on one side of the sense resistor, and the other side of the sense resistor is connected to the electronic load. For the ±2 A and 0.25–1 A monitoring, two tests are performed for each rail. All tests were done at an ambient temperature of 25°C.

The following list provides the test procedure for Noise floor:

  1. Short both sides of the sense resistor to ground.
  2. Open Code Composer Studio (CCS) to run the MSP430 software.
  3. Configure the MSP430 software for either internal or external ADC, and set the desired ADC channel.
  4. Capture and plot 1000 plots by using memory export and Microsoft Excel to convert the digital data to the ADC voltage reading using the ADC conversion equation.
  5. Calculate the actual current reading by solving the linear equation
    Equation 8. I n p u t   C u r r e n t   A c t u a l = A D C   V o l t a g e   R e a d i n g - 0.2 V G a i n × S e n s e   R e s i s t o r
  6. Repeat for the rest of the other current inputs.

The following list provides the test procedure for Linearity

  1. Connect the power supply to the desired terminal block as shown in Figure 3-3.
  2. Open CCS to run the MSP430 software.
  3. Configure the MSP430 software for either internal or external ADC, and set the desired ADC channel.
  4. Capture and export 1000 measurements by using the memory export and Microsoft Excel to convert the digital data to the voltage reading using the ADC conversion equation.
  5. Calculate the actual current reading by solving the linear equation:
    Equation 9. I n p u t   C u r r e n t   A c t u a l = A D C   V o l t a g e   R e a d i n g - 0.2 V G a i n × S e n s e   R e s i s t o r
  6. Repeat over the rest of the current range.