71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
HARDWARE DESCRIPTION
Hardware Overview
The TERIDIAN 71M6511 single chip single-phase 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 71M6511/6511H 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 71M6511 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,
I2C 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 TERIDIAN 71M6511 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 four input signals that are applied to the pins IA, VA, and IB 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 pins IA, VA, and IB, are selected.
During the alternate multiplexer cycle, the temperature signal (TEMP) is selected, along with the other signal sources
shown in Table 1.
Alternate multiplexer cycles are usually performed infrequently (every second or so). VA is not replaced in the alternate multi-
plexer cycles. Missing samples due to alternate multiplexer cycles are automatically interpolated by the CE.
Channels used from MUX
Sequence
Channels used from alternative
MUX Sequence
EQU
States 0 → 3
States 0 → 3
0
1
2
3
-
0
1
2
-
3
-
000
001
IA
IA
VA
VA
IB
IB
TEMP
TEMP
VA
VA
-
IB
-
Table 1: Inputs Selected in Regular and Alternate Multiplexer Cycles
In a typical application, the IA input is connected to a current transformer that senses the line current. VA is typically connected
to a voltage sensor through resistor dividers. IB may be connected to a second current transformer, e.g. for optional tamper
detection.
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