Datasheet

DS_6612_001 78M6612 Data Sheet

Rev 2 7

1 Hardware Description

1.1 Hardware Overview

The Teridian 78M6612 single-chip measurement and monitoring IC integrates all the primary AC

measurement and control blocks required to implement a solid-state electricity Power and Energy

Measurement function. The 78M6618 includes:

• A four-input analog front end (AFE)

• An independent digital computation engine (CE)

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

• A precision voltage reference

• A temperature sensor

• LCD drivers

• RAM and Flash memory

• A real time clock (RTC)

• A variety of I/O pins

Various current sensor technologies are supported including Current Transformers (CT), and Resistive

Shunts.

In a typical application, the 32-bit compute engine (CE) of the 78M6612 sequentially processes the

samples from the analog inputs on pins IA, VA, IB, VB and performs calculations to measure active

energy (Wh), reactive energy (VARh), A

h, and V

h for four-quadrant measurement. 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 real time clock function allows the 78M6612 to

record time of use (TOU) measurement information for multi-rate applications and to time-stamp events.

Measurements can be displayed on 3.3 V LCDs if desired. Flexible mapping of LCD display segments

will facilitate utilization of existing custom LCDs. Design trade-off between number of LCD segments vs.

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 standards. Temperature-dependent external components such as crystal oscillator,

current transformers (CTs), and their corresponding signal conditioning circuits can be characterized and

their correction factors can be programmed to produce measurements with exceptional accuracy over the

industrial temperature range.

A block diagram of the IC is shown in Figure 1. A detailed description of various functional blocks follows.