AMC131M02DFMR datasheet(74/89 Pages) TI

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9.2 Typical Application

This section describes a typical three-phase energy measurement front-end using the AMC131M02. The ADC

samples the outputs of resistive current sensors (shunts) and voltage dividers to measure the current and

voltage of each leg of the AC mains. The design can achieve high accuracy across a wide input current range

(0.05 A–100 A) and supports high sampling frequencies necessary for advanced power-quality features, such

as individual harmonic analysis. Using the AMC131M02 to sample the voltages and currents per phase provides

designers greater flexibility in the choice of metrology microcontrollers (MCU) when compared to an integrated

system-on-a-chip (SoC) and dedicated application-specific products.

Figure 9-4 illustrates the front-end for a three-phase energy measurement design. In this design, one

AMC131M02 per phase measures the current and voltage for this respective phase, providing galvanic isolation

from phase to phase. This isolation is critical because the voltage level in a typical case can be in the order

of 220 V on one phase and –220 V at another phase. If only one ADC for multiple phases is used, a voltage

difference in the order of 440 V between two adjacent ADC inputs can appear, potentially destroying the device.

The design also includes a fourth ADC to monitor the current in the neutral line. Assuming the system ground

for the metering front-end is connected to the neutral line, this ADC can be a non-isolated device such as the

ADS131M02. This fourth device is optional and is typically used if tamper detection is a concern.

RC antialiasing filters are not given in Figure 9-4 for simplicity, but are recommended for all channels.

The microcontroller uses the SPI port to communicate with the four ADC devices, and provides a clock to all

ADC devices at the respective CLKIN pins. Four of the microcontroller I/O pins (CS_A, CS_B, CS_C, and CS_D)

generate the SPI CS signals. The SCLK, DIN, and DOUT connections are shared between all ADC devices. To

simplify the figure, these connections are not shown in detail.

AMC131M02

SBASA56 – SEPTEMBER 2023

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