TIDUF27A February   2025  – March 2025 AMC131M03 , MSPM0G1507

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
    2. 1.2 End Equipment
    3. 1.3 Electricity Meter
    4. 1.4 Power Quality Meter, Power Quality Analyzer
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Voltage Measurement Analog Front End
      2. 2.2.2 Analog Front End for Current Measurement
      3. 2.2.3 XDS110 Emulator
      4. 2.2.4 Bluetooth® Data Transmission
      5. 2.2.5 Bluetooth® Connection Between Two Modules
      6. 2.2.6 Bluetooth® to UART Connection
      7. 2.2.7 Magnetic Tamper Detection With TMAG5273 Linear 3D Hall-Effect Sensor
    3. 2.3 Highlighted Products
      1. 2.3.1  MSPM0G3507
      2. 2.3.2  AMC131M03
      3. 2.3.3  CDC6C
      4. 2.3.4  RES60A-Q1
      5. 2.3.5  TPS3702
      6. 2.3.6  TPD4E05U06
      7. 2.3.7  ISOUSB111
      8. 2.3.8  LMK1C1104
      9. 2.3.9  MSP432E401Y
      10. 2.3.10 TPS709
      11. 2.3.11 TMAG5273
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 Clocking System
        1. 3.1.1.1 BAW Oscillator
        2. 3.1.1.2 Crystal Oscillator
        3. 3.1.1.3 PWM
        4. 3.1.1.4 Clock Buffers
      2. 3.1.2 SPI Bus Configuration
      3. 3.1.3 Jumper Settings for LED and UART
    2. 3.2 Software Requirements
      1. 3.2.1 UART for PC GUI Communication
      2. 3.2.2 Direct Memory Access (DMA)
      3. 3.2.3 ADC Setup
      4. 3.2.4 Calibration
    3. 3.3 Test Setup
      1. 3.3.1 Connections to the Test Setup
      2. 3.3.2 Power Supply Options and Jumper Settings
        1.       51
      3. 3.3.3 Cautions and Warnings
    4. 3.4 Test Results
      1. 3.4.1 Electricity Meter Metrology Accuracy Results
      2. 3.4.2 Radiated Emissions Performance
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 PCB Layout Recommendations
        1. 4.1.3.1 Layout Prints
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author
  12. 6Revision History

2.2.1 Voltage Measurement Analog Front End

The nominal voltage from the Mains in many regions of the world varies from 100V–240V so the voltage needs to be scaled down to be sensed by an ADC. Figure 2-2 shows the analog front end used for this voltage scaling, voltage is applied at J11 for Phase C, similar circuitry is used for each of the Phases A and B.

TIDA-010244 Analog Front End for Voltage Inputs Figure 2-2 Analog Front End for Voltage Inputs

The analog front end for voltage inputs has a voltage divider network (R70, R71, R72, and R69), and an RC low-pass filter (R68, R73, C56, C57) and C58, as shown in Figure 2-2.

Optionally, a high-precision resistor divider RES60A (U17) is added. This resistor divider lowers the voltage with the ratio 1000:1 and is an alternative to the discrete voltage divider with R70, R71, R72, and R69. To use the RES60A instead of the series resistor chain divider network, change the following components:

  • Remove R69, R70, R71, and R72
  • Place R127 (0Ω)
  • Place RES60A

Follow similar steps for Phase A and B.

At lower currents, voltage-to-current crosstalk affects active energy accuracy much more than voltage accuracy if power offset calibration is not performed. To maximize the accuracy at these lower currents, in this design the entire ADC range is not used for the voltage channels. The reduced ADC range for the voltage channels in this design still provides more than enough accuracy for measuring voltage. Equation 1 shows how to calculate the range of differential voltages fed to the voltage ADC channel for a given Mains voltage and selected voltage divider resistor values.

Equation 1. V A D C _ S w i n g , V o l t a g e = ± V R M S × 2 R 69 R 70 + R 71 +   R 72 +   R 69

Based on this formula and the selected resistor values in Equation 1, for a Mains voltage of 120V (as measured between the line and neutral), the input signal to the voltage ADC has a voltage swing of ±128.47mV (90.8mVRMS). For a Mains voltage of 230V (as measured between the line and neutral), the 230V input to the front-end circuit produces a voltage swing of ±246.23mV (174.11mVRMS). The ±128.47mV and the ±246.23mV voltage ranges are both well within the –1.3V to + 2.7V range (for GAIN = 1, see the recommended operating conditions section of the AMC131M03 3-Channel, 64-kSPS, Simultaneous-Sampling, 24-Bit, Reinforced Isolated Delta-Sigma ADC With Integrated DC/DC Converter data sheet), that can be sensed by the ADC.