71M6541F datasheet(11/166 Pages) MAXIM

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71M6541D/F/G and 71M6542F/G Data Sheet

Rev 2

Hardware Description

2.1

Hardware Overview

The Teridian 71M6541D/F/G and 71M6542F/G single-chip energy meter ICs integrate all primary

functional blocks required to implement a solid-state residential electricity meter. Included on the chip

are:

•

An analog front end (AFE) featuring a 22-bit second-order sigma-delta ADC

•

An independent 32-bit digital computation engine (CE) to implement DSP functions

•

An 8051-compatible microprocessor (MPU) which executes one instruction per clock cycle (80515)

•

A precision voltage reference (VREF)

•

A temperature sensor for digital temperature compensation:

Metrology digital temperature compensation (MPU)

Automatic RTC digital temperature compensation operational in all power states

•

LCD drivers

•

RAM and Flash memory

•

A real time clock (RTC)

•

A variety of I/O pins

•

A power failure interrupt

•

A zero-crossing interrupt

•

Selectable current sensor interfaces for locally-connected sensors as well as isolated sensors (i.e.,

using the 71M6x01 companion IC with a shunt resistor sensor)

•

Resistive Shunt and Current Transformers are supported

Resistive Shunts and Current Transformers (CT) current sensors are supported. Resistive shunt current

sensors may be connected directly to the 71M654x device or isolated using a companion 71M6x01

isolator IC in order to implement a variety of single-phase / split-phase (71M6541D/F/G) or two-phase

(71M6542F/G) metering configurations. An inexpensive, small size pulse transformer is used to isolate

the 71M6x01 isolated sensor from the 71M654x. The 71M654x performs digital communications bi-

directionally with the 71M6x01 and also provides power to the 71M6x01 through the isolating pulse

transformer. Isolated (remote) shunt current sensors are connected to the differential input of the

71M6x01. Included on the 71M6x01 companion isolator chip are:

•

Digital isolation communications interface

•

An analog front end (AFE)

•

A precision voltage reference (VREF)

•

A temperature sensor (for digital temperature compensation)

•

A fully differential shunt resistor sensor input

•

A pre-amplifier to optimize shunt current sensor performance

•

Isolated power circuitry obtains dc power from pulses sent by the 71M654x

In a typical application, the 32-bit compute engine (CE) of the 71M654x sequentially processes the samples

from the voltage inputs on analog input pins and from the external 71M6x01 isolated sensors and performs

calculations to measure active energy (Wh) and reactive energy (VARh), as well as A

2h, and V2h for four-

quadrant metering. These measurements are then accessed by the MPU, processed further and output

using the peripheral devices available to the MPU.

In addition to advanced measurement functions, the clock function allows the 71M6541D/F/G and

71M6542F/G to record time-of-use (TOU) metering information for multi-rate applications and to time-

stamp tamper or other events. Measurements can be displayed on 3.3 V LCDs commonly used in low-tem-

perature environments. An on-chip charge pump is available to drive 5 V LCDs. Flexible mapping of LCD

display segments facilitate integration of existing custom LCDs. Design trade-off between the number of

LCD segments and DIO pins can be implemented in software to accommodate various requirements.

In addition to the temperature-trimmed ultra-precision voltage reference, the on-chip digital temperature

compensation mechanism includes a temperature sensor and associated controls for correction of unwanted

temperature effects on measurement and RTC accuracy, e.g., to meet the requirements of ANSI and IEC

71M6541F Datasheet(PDF) 11 Page - Maxim Integrated Products

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