Texas Instruments TIDA-010037 Manual

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Design Guide: TIDA-010037
High-Accuracy Split-Phase CT Electricity Meter Reference
Design Using Standalone ADCs
Description
This reference design implements Class 0.1 split-
phase energy measurement using high-performance,
multi-channel analog-to-digital converters (ADC). The
ADC samples current transformers (CT) at 8 kHz to
measure the current and voltage of each leg of the AC
mains. The reference design achieves high accuracy
across a wide input current range (0.05–100 A) and
supports high sampling frequencies necessary for
power quality features such as individual harmonic
analysis. An ADC sample rate of 32 ksps can be
acheived by disabling some software functions.
Independent ADCs provide flexibility in the choice of
metrology microcontrollers compared to integrated
SoCs. This reference design uses a SimpleLink
ARM ® Cortex ® -M4 host microcontroller for metrology.
The necessary software functionality is implemented
in the ADC Energy Metrology library. The software
library can be compiled with Code Composer Studio
or IAR Embedded Workbench
Resources
TIDA-010037
ADS131M04, MSP432P4111
TPS3840, TPS25921l, THVD1500
ISO7731B, TRS3232E
ADC Energy Metrology Library
Ask our TI E2E
TIDUEM8B – MARCH 2019 – REVISED FEBRUARY 2021
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Load
Phase A Phase B
5V_IN
VCC
TPS709
GND GND
TPS25921L
5V_LMT
TVS1800
VCC
RESET VCC
VDD ADS131M04
GND
GND
TPS3840
CT
+
CT I
A 6' ADC
-
CSn
+
SCLK
CT I ADC
B 6'
DIN
-
DOUT
+
ADC
V 6'
A
-
DRDY
+
6' ADC
V
B
-
CLKIN
Phase A Phase B
Source From Utility
Copyright © 2021 Texas Instruments Incorporated
Features
• Split-phase metrology for electricity meters that
meets ANSI C12.20 Class 0.1 active energy
accuracy requirements across 10000:1 input range
• Active and reactive energy and power, root mean
square (RMS) current and voltage, power factor,
and line-frequency calculations
• Isolated RS-232 and RS-485 with 5-kV
isolation
• Communications module expansion with current
limit and overvoltage and undervoltage protection
• Tested across 50 mA to 100 A input range
• High active energy accuracy still obtained when
ADC sample rate increased to 32 ksps
• Software for energy metrology and displaying
results on a Windows
Applications
• Electricity meter
• Power quality meter
• Power quality analyzer
+
A
B
-
TOTAL kWh
VCC
DVCC
Lx
Active
DVSS GPIO
GND
ISO-DVCC
VCC
Reactive
GPIO ISO-GND
ISO7720
VCC
ISO-ACTIVE
GND
ISO-REACTIVE
RESET RST/NMI
MSP432P4111
GND
GPIO
SPI CLK
RS232_VCC
VCC
SPI MOSI
SPI MISO RS232_GND
GND
TPS709
RGND
ISO7731 B
Interruptible GPIO
UART2 TX
TRS3232E
UART2 RX
GPIO
SMCLK
GND
Lx/PMAP GPIO
Board
RE
Lx/PMAP GPIO
Header to
RGND
WE
Lx/PMAP GPIO External
VCC3
THVD1500
Lx/PMAP GPIO Radio/Radio
Module
5V_LMT
High-Accuracy Split-Phase CT Electricity Meter Reference Design Using
Description
RMS
®
PC GUI.
DTR
RTS
RS-232
Connection
RS-485
Connection
Standalone ADCs
1