2 analog front end (afe), Analog front end (afe) – Rainbow Electronics 71M6542G User Manual

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v1.1

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

∆Σ ADC

CONVERTER

VREF