TIDUF98 October   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 End Equipment
      1. 1.1.1 Electricity Meter
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 ADS131M03
      2. 2.2.2 MSPM0L2228
      3. 2.2.3 THVD1400
      4. 2.2.4 ISO6731
      5. 2.2.5 DRV5032
    3. 2.3 Design Considerations
      1. 2.3.1 Design Hardware Implementation
        1. 2.3.1.1 Analog Inputs
          1. 2.3.1.1.1 Voltage Measurement Analog Front End
          2. 2.3.1.1.2 Current Measurement Analog Front End
      2. 2.3.2 Energy Metrology Software
        1. 2.3.2.1 Software Architecture
        2. 2.3.2.2 Setup
          1. 2.3.2.2.1 Clocking Scheme
          2. 2.3.2.2.2 SPI
          3. 2.3.2.2.3 UART Setup for GUI Communication
          4. 2.3.2.2.4 Real-Time Clock
          5. 2.3.2.2.5 LCD Controller
          6. 2.3.2.2.6 Direct Memory Access
    4. 2.4 Hardware, Software, Testing Requirements, and Test Results
      1. 2.4.1 Required Hardware and Software
        1. 2.4.1.1 Cautions and Warnings
        2. 2.4.1.2 Hardware
          1. 2.4.1.2.1 Connections to the Test Setup
          2. 2.4.1.2.2 Power Supply Options and Jumper Settings
        3. 2.4.1.3 Calibration
      2. 2.4.2 Testing and Results
        1. 2.4.2.1 Test Setup
          1. 2.4.2.1.1 Viewing Metrology Readings and Calibration
            1. 2.4.2.1.1.1 Viewing Results From LCD
            2. 2.4.2.1.1.2 Viewing Results From PC GUI
        2. 2.4.2.2 Electricity Meter Metrology Accuracy Testing
        3. 2.4.2.3 Electricity Meter Metrology Accuracy Results
  9. 3Design Files
    1. 3.1 Schematics
    2. 3.2 Bill of Materials
    3. 3.3 PCB Layout Recommendations
      1. 3.3.1 Layout Prints
    4. 3.4 Altium Project
    5. 3.5 Gerber Files
    6. 3.6 Assembly Drawings
  10. 4Related Documentation
    1. 4.1 Trademarks
  11. 5About the Authors

3.3 PCB Layout Recommendations

For this design, the following general guidelines need to be followed:

  • Place decoupling capacitors close to the associated pins.
  • Use ground planes instead of ground traces and minimize the cuts in the ground plane, especially near the ADS131M03 device. In this design, there is a ground plane on both the top and bottom layer; for this situation, make sure that there is good stitching between the planes through the liberal use of vias.
  • Keep the two traces to the inputs of an ADC channel symmetrical and as close as possible to each other.
  • For the ADS131M03 device, place the 0.1μF capacitor closer to the AVDD pin than the 1μF capacitor. Do the same thing also for the 0.1-μF and 1-μF capacitors connected to DVDD.
  • Minimize the length of the traces used to connect the crystal to the MCU. Place guard rings around the leads of the crystal and ground the crystal housing. In addition, there must be clean ground underneath the crystal and avoid placing any traces underneath the crystal. Also, keep high-frequency signals away from the two MCU crystals.
  • Use wide traces for power-supply connections.
  • Use a different ground plane for the isolated RS-485. This other ground plane is at the potential of the RS-485 ground and not the GND used elsewhere in the board.
  • Make sure that the recommended clearance and creepage spacing are met for the ISO6731.