AMC131M02 datasheet(76/89 Pages) TI

76 / 89 page

9.2.1 Design Requirements

Table 9-2 lists the design requirements for a three-phase metrology application.

Table 9-2. Key System Specifications

FEATURES

DESCRIPTION

Number of phases

3 phase (requires measurement of three voltages and three currents)

E-meter accuracy class

Class 0.1

Current sensor

Shunt resistor

Current range

0.05 A–100 A

System nominal frequency

50 Hz or 60 Hz

Measured parameters

•

Active, reactive, apparent power, and energy

•

Root-mean-square (RMS) current and voltage

•

Power factor

•

Line frequency

9.2.2 Detailed Design Procedure

Figure 9-5 illustrates phase A of a three-phase energy meter. The other AMC131M02 devices that monitor

phases B and C are connected in a similar way. The phase A current, ISHUNT, is sensed with a shunt resistor

(RSHUNT) using channel 0 of the ADC (AIN0N, AIN0P). One terminal of the shunt becomes the isolated

ground ISO_GND of the circuit and is connected to the ground pin HGND (pin 5) of the isolated side of the

AMC131M02. The phase A to neutral voltage VPHASEA is sensed with a resistor divider connected to channel 1,

and the AIN1N pin is also connected to the ISO_GND node. The high side of the resistor divider is connected to

the neutral line, the mid-point of the resistor divider is connected to the positive ADC input AIN1P, and the low

side of the resistor divider (which is sensing the ISO_GND node) is connected to the negative input AIN1N of

channel 1; therefore, the negative phase voltage is measured at channel 1. Thus, voltages measured by channel

1 of the AMC131M02 are opposite in sign to the phase voltage VPHASEA and the phase current ISHUNT, which is a

classic approach in single-phase and poly-phase metering.

The selection of the shunt resistor value is made based on the manufacturer and current range required for

energy measurements. The voltage divider resistors for the voltage channel are selected to make sure the mains

voltage is divided down to adhere to the normal input voltage ranges of the AMC131M02.

In this design, the AMC131M02 interacts with an MCU in the following manner:

• The MCU provides the CLKIN clock to the AMC131M02

• When new ADC conversion data are ready, the AMC131M02 asserts the DRDY pin, which alerts the MCU

that new samples are available

• After being alerted of new conversion data, the MCU retrieves the voltage and current samples from the

AMC131M02 through the SPI interface

AMC131M02

SBASA56 – SEPTEMBER 2023

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