71M6541D Datasheet, PDF (12/166 Pages) Maxim Integrated Products – 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs

71M6541D/F/G and 71M6542F/G Data Sheet
standards. Temperature-dependent external components such as crystal oscillator, resistive shunts, 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 configuration
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 IC is shown in
Figure 1.
2.2 Analog Front End (AFE)
The AFE functions as a data acquisition system, controlled by the MPU. When used with locally
connected sensors, as seen in Figure 2, the analog input signals (IAP-IAN, VA and IBP-IBN) are
multiplexed to the ADC input and sampled by the ADC. The ADC output is decimated by the FIR filter
and stored in CE RAM where it can be accessed and processed by the CE.
See Figure 6 for the multiplexer sequence corresponding to Figure 2. See Figure 35 for the meter
configuration corresponding to Figure 2.
I_LINE
I_LINE
IAP
CT
or
Local
Shunt
IAN
VADC10 (VA)
MUX
VREF
VREF
VADC
∆Σ ADC
CONVERTER
VREF
FIR
22
CE RAM
IN*
IBP
CT
IBN
71M6541D/F
*IN = Optional Neutral Current
Figure 2. 71M6541D/F/G AFE Block Diagram (Local Sensors)
11/5/2010