A Maxim Integrated Products Brand
71M6513/71M6513H
3-Phase Energy Meter IC
DATA SHEET
SEPTEMBER 2011
HARDWARE DESCRIPTION
Hardware Overview
The 71M6513 single-chip polyphase meter integrates all primary functional blocks required to implement a solid-state
electricity meter. Included on chip are an analog front end (AFE), an 8051-compatible microprocessor (MPU) which executes
one instruction per clock cycle (80515), an independent 32-bit digital computation engine (CE), a voltage reference, a
temperature sensor, LCD drivers, RAM, flash memory, a real time clock (RTC), and a variety of I/O pins. Various current
sensor technologies are supported including Current Transformers (CT), Resistive Shunts, and Rogowski (di/dt) Coils.
In addition to advanced measurement functions, the real time clock function allows the 71M6513/6513H to record time of use
(TOU) metering information for multi-rate applications. Measurements can be displayed on either a 3V or a 5V LCD. Flexible
mapping of LCD display segments will facilitate integration with any LCD format. The design trade-off between the number of
LCD segments and DIO pins can be flexibly configured using memory-mapped I/O to accommodate various requirements.
The 71M6513 includes several I/O peripheral functions that improve the functionality of the device and reduce the component
count for most meter applications. The I/O peripherals include two UARTs, digital I/O, comparator inputs, LCD display drivers,
2
I C interface and an optical/IR interface.
One of the two internal UARTs (UART1) is adapted to support an Infrared LED with internal drive output and sense input but it
can also function as a standard UART.
A block diagram of the chip is shown in Figure 1. A detailed description of various hardware blocks follows.
Analog Front End (AFE)
The AFE of the 71M6513 Power Meter IC is comprised of an input multiplexer, a delta-sigma A/D converter with a voltage
reference, followed by an FIR filter. A block diagram of the AFE is shown in Figure 3.
Multiplexer
The input multiplexer supports eight input signals that are applied to the pins IA, VA, IB, VB, IC, VC, and V3 plus the output of
the internal temperature sensor. The multiplexer can be operated in two modes:
•
•
During a normal multiplexer cycle, the signals from the six pins IA, VA, IB, VB, IC, and VC are selected.
During the alternate multiplexer cycle, the temperature signal (TEMP) and the additional monitor input, V3, are
selected, along with the other signal sources shown in Table 1: Inputs Selected in Regular and Alternate Multiplexer
Alternate multiplexer cycles are usually performed infrequently (every second or so). VA, VB, and VC are not replaced in the
alternate multiplexer cycles. In some equations, currents must be delayed in allpass networks and therefore cannot be
replaced in the alternate selection. Missing samples due to alternate multiplexer cycles are automatically interpolated by the
CE.
Regular multiplexer sequence
Mux State:
0
IA
1
VA
2
IB
3
VB
4
IC
5
VC
Alternate multiplexer sequence
Mux State:
0
TEMP
1
VA
2
V3
3
VB
4
IC
5
VC
Table 1: Inputs Selected in Regular and Alternate Multiplexer Cycles
In a typical application, the IA, IB, and IC inputs are connected to current transformers that sense the current on each phase of
the line voltage. VA, VB, and VC are typically connected to voltage sensors through resistor dividers.
The Multiplexer Control Circuit handles the setting of the multiplexer. The function of the Multiplexer Control Circuit is
governed by the I/O RAM registers
MUX_ALT
(0x2005[2]),
EQU
(0x2000[7:5]), and
MUX_DIV
(0x2002[7:6]).
MUX_DIV
controls
the number of samples per cycle. It can request 2, 3, 4, or 6 multiplexer states per cycle.
© 2005-2011 Teridian Semiconductor Corporation
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