71M6531D Datasheet, PDF (10/115 Pages) Teridian Semiconductor Corporation – Energy Meter IC

Data Sheet 71M6531D/F-71M6532D/F
FDS 6531/6532 005
1 Hardware Description
1.1 Hardware Overview
The Teridian 71M6531D/F and 71M6532D/F single-chip energy meters integrates all primary functional
blocks required to implement a solid-state electricity meter. Included on the chips are:
• 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), Resistive Shunts
and Rogowski coils.
In a typical application, the 32-bit compute engine (CE) of the 71M6531D/F and 71M6532D/F sequentially
process the samples from the voltage inputs on pins IA, VA, IB, VB and performs calculations to measure
active energy (Wh) and reactive energy (VARh), as well as A²h 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 real time clock function allows the 71M6531D/F and
71M6532D/F to record time of use (TOU) metering information for multi-rate applications and to time-
stamp tamper events. Measurements can be displayed on 3.3 V LCDs commonly used in low-tem-
perature environments. Flexible mapping of LCD display segments facilitate integration of existing cus-
tom 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 un-
wanted temperature effects on measurement and RTC accuracy, e.g. to meet the requirements of ANSI
and IEC standards. Temperature-dependent external components such as a crystal oscillator, current
transformers (CTs) and their corresponding signal conditioning circuits can be characterized and their
correction factors can be programmed to produce electricity meters with exceptional accuracy over the
industrial temperature range.
One of the two internal UARTs is adapted to support an Infrared LED with internal drive and sense confi-
guration and can also function as a standard UART. The optical output can be modulated at 38 kHz.
This flexibility makes it possible to implement AMR meters with an IR interface. A block diagram of the
71M6531D/F IC is shown in Figure 1. A block diagram of the 71M6532D/F IC is shown in Figure 2.
1.2 Analog Front End (AFE)
The AFE consists of an input multiplexer, a delta-sigma A/D converter and a voltage reference.
1.2.1 Signal Input Pins
All analog signal input pins are sensitive to voltage. In the 71M6531D/F, the VA and VB pins, as well as the
IA and IB pins are single-ended. In the 71M6532D/F, the IAP/IAN and IBP/IBN pins can be programmed
individually to be differential (see I/O RAM bit SEL_IAN and SEL_IBN) or single-ended. The differential sig-
nal is applied between the IAP and IAN input pins and between the IBP and IBN input pins. Single-ended
signals are applied to the IAP and IBP input pins whereas the common signal, return, is the V3P3A pin.
When using the differential mode, inputs can be chopped, i.e. a connection from V3P3A to IAP or IAN (or
IBP an IBN, respectively) alternates in each multiplexer cycle.
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