Figure 2-1 depicts the MSPM0G3507 and AMC131M03-based three-phase energy measurement application block diagram.

On each phase (or line) the line-to-neutral voltage is directly measured, as well as the current for each line (3 phases) and through the N (Neutral) wire; hence, both 3-phase, 3-wire (3P3W) or 3-phase, 4-wire with Neutral (3P4W) configurations are supported by default. By not using some phases, this reference design can also be used in a split-phase (leave open Phase C) or single-phase (leave open Phase B and C) configuration. In the TIDA-010244 block diagram, shunt sensors connect to each of the 3 phases for the current measurement while a simple voltage divider is used for dividing down the corresponding voltage of each line. The selection of the shunt is made based on the current range required for the energy measurements, while minimizing power dissipation in the shunt at high currents. Values in the range of 150μ? to 200μ? are common, assuming up to 100A or 120A maximum current per phase are to be measured.

In this design, the four AMC131M03 or AMC131M02 devices interact with the MSPM0+ MCU in the following manner:

1. Three different clock signals are fed to a 4-channel output LVCMOS buffer LMK1C1104 to obtain 4 identical in-phase clock signals CLKIN1 through CLKIN4, making sure all ADCs run and collect data samples synchronized to each other.
   1. TI BAW oscillator CDC6C provides a high-precision clock signal with 8.192MHz to both LMK1C1104 and MSPM0G3507 devices (default option).
   2. An external 16.384MHz crystal oscillator (XTAL) supplies the MSPM0G3507 HFXIN and HFXOUT pins and runs through an internal divider by 2 to create the M0_CLKOUT signal at 8.192MHz (when TI BAW is not populated). M0_CLKOUT is then connected to the LMK1C1104 clock buffer.
   3. A PWM signal from the MSPM0G3507 can be used to supply the clock buffers for evaluation purposes. To enable the PWM signal one of the previously mentioned clock devices needs to be connected to HFXIN and HFXOUT (optional).
2. The 4 outputs of LMK1C1104 are fed to the four CLKIN1 through CLKIN4 input pins (one per ADC device).
3. Each of the four AMC131M03 or AMC131M02 devices divides the CLKIN input by 2 and uses that value as the delta-sigma modulation clock.
4. The SPI_SCK (SPU Bus clock) signal (output from the MCU being the SPI controller) is input to a second 4-channel output LVCMOS buffer LMK1C1104 to obtain four identical in-phase clock signals for the SPI data transfer.
5. The four SPI_SCK lines SCLK1 through SCLK4 are fed to the SCLK input of each ADC, making sure all ADCs run synchronously on the shared SPI bus.
6. Four separate CS lines are used, these are automatically generated and controlled by the SPI peripheral of the MSPM0+ MCU.
7. When new ADC samples are ready, each AMC131M03 asserts the DRDY output pin (DRDY1 through DRDY4), which alerts the MCU that new data samples are available.
8. After detecting the DRDY falling edge, the MSPM0+ MCU uses one SPI and two of the DMA channels in the DMA module to read in the voltage and current samples from each AMC131M0X device. The four standalone ADCs generate the four DRDY signals simultaneously but because the ADCs share the same SPI bus, the ADCs are being read out sequentially by the MCU.
9. The MCU also communicates to a PC GUI through the USB Type-C interface over the XDS110 debugger on the board or an external FTDI connector.
10. ACT and REACT output signals from the MCU represent the active and reactive energy pulses used for accuracy measurement and calibration. Both are key signals needed for calibrating the electricity meter against a reference meter.

The MSPM0+ MCU has internal Power-on reset (POR) and POR as well as Brownout reset (BOR) supply monitor with four configurable threshold voltages.

This reference design can be powered either by applying 5V through the USB Type-C connector or the marked headers or 3.3V at the designated header pins. See Section 3.3.2 for more details on the proper jumper connections for powering the board.

The USB Type-C interface can be used to program and debug the MSPM0G3507. This interface is isolated and can be used to provide 5V from the USB power to the system. If the 5V option is chosen, the isolation of the USB Type-C interface is not in effect.

This reference design also comes with two options of transmitting the metrology parameters data over Bluetooth using either the CC2340 Bluetooth low energy subsystem with all passives (discrete implementation) or a CC2340-based Bluetooth module.

Figure 2-1 MSPM0G3507 and AMC131M03-Based Three-Phase Energy Measurement Block Diagram