2 System Overview
2.1 Block Diagram
and
depict block diagrams that show the high-level interface used for an ADS131M04-
based split-phase energy measurement application. For the two-voltage configuration, the line-to-neutral voltage
is directly measured for each line wire. For the one-voltage configuration, in comparison, only the line-to-line
voltage is directly measured instead of the line-to-neutral voltages.
6'
ADC
6'
ADC
-
Source From Utility
Load
Phase A
Phase A
N
e
u
tra
l
+
+
-
ADS131M04
N
e
u
tra
l
SCLK
DIN
DOUT
DRDY
VCC
GND
6'
ADC
6'
ADC
-
+
+
-
SPI MISO
GPIO
Interruptible GPIO
SPI CLK
SPI MOSI
CLKIN
VDD
GND
SMCLK
RESET VCC
CSn
Phase B
Phase B
I
A
I
B
CT
CT
+
-
TOTAL
A
B
kWh
VCC
GND
Lx
MSP432P4111
GPIO
GPIO
VCC
GND
ISO-DVCC
ISO-GND
ISO-ACTIVE
ISO-REACTIVE
ISO7720
DVCC
DVSS
Active
Reactive
TPS3840
VCC
RESET
CT
GND
RST/NMI
TPS709
GND
VCC
GND
5V_IN
TVS1800
TPS25921L
5V_LMT
Lx/PMAP GPIO
UART2 TX
UART2 RX
RS-232
Connection
ISO7731 B
VCC
GND
TPS709
TRS3232E
DTR
RTS
RGND
RS232_VCC
RS232_GND
Board
Header to
External
Radio/Radio
Module
5V_LMT
GND
Lx/PMAP GPIO
Lx/PMAP GPIO
Lx/PMAP GPIO
THVD1500
RS-485
Connection
GPIO
RE
WE
RGND
VCC3
V
B
V
A
Figure 2-1. TIDA-010037 Block Diagram, Two-Voltage Configuration
6'
ADC
6'
ADC
-
Source From Utility
Load
Phase A
Phase A
N
e
u
tra
l
+
+
-
ADS131M04
N
e
u
tra
l
SCLK
DIN
DOUT
DRDY
VCC
GND
6'
ADC
6'
ADC
-
+
+
-
SPI MISO
GPIO
Interruptible GPIO
SPI CLK
SPI MOSI
CLKIN
VDD
GND
SMCLK
RESET VCC
CSn
Phase B
Phase B
V
I
A
I
B
CT
CT
+
-
TOTAL
A
B
kWh
VCC
GND
Lx
MSP432P4111
GPIO
GPIO
VCC
GND
ISO-DVCC
ISO-GND
ISO-ACTIVE
ISO-REACTIVE
ISO7720
DVCC
DVSS
Active
Reactive
TPS3840
VCC
RESET
CT
GND
RST/NMI
TPS709
GND
VCC
GND
5V_IN
TVS1800
TPS25921L
5V_LMT
Lx/PMAP GPIO
UART2 TX
UART2 RX
RS-232
Connection
ISO7731 B
VCC
GND
TPS709
TRS3232E
DTR
RTS
RGND
RS232_VCC
RS232_GND
Board
Header to
External
Radio/Radio
Module
5V_LMT
GND
Lx/PMAP GPIO
Lx/PMAP GPIO
Lx/PMAP GPIO
THVD1500
RS-485
Connection
GPIO
RE
WE
RGND
VCC3
Figure 2-2. TIDA-010037 Block Diagram, One-Voltage Configuration
In the diagrams, a current sensor connects to the current channels and a simple voltage divider is used for the
corresponding voltage. The CT has an associated burden resistor that must be connected at all times to protect
the measuring device. The selection of the CT and the burden resistor is made based on the manufacturer and
current range required for energy measurements.
System Overview
TIDUEM8B – MARCH 2019 – REVISED FEBRUARY 2021
High-Accuracy Split-Phase CT Electricity Meter Reference Design Using
Standalone ADCs
5
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