78M6612 Data Sheet
DS_6612_001
1 Hardware Description
1.1 Hardware Overview
The Teridian 78M6612 single-chip measurement unit integrates all primary functional blocks required to
implement a solid-state electricity Power and Energy Measurement function. Included on chips are:
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An analog front end (AFE)
An independent digital computation engine (CE)
An 8051-compatible microprocessor (MPU) which executes one instruction per clock cycle (80515)
A 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 voltage inputs on pins IA, VA, IB, VB and performs calculations to measure active
energy (Wh), reactive energy (VARh), A2h, and V2h 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, if desired.
One of the two internal UARTs is adapted to support an Infrared LED with internal drive and sense
configuration, and can also function as a standard UART. The optical output can be modulated at
38 kHz. A block diagram of the IC is shown in Figure 1. A detailed description of various functional
blocks follows.
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Rev. 1.2
TERIDIAN [ TERIDIAN SEMICONDUCTOR CORPORATION ]
