Rainbow Electronics 78M6631 - Manual (Page 8)

78M6631 Data Sheet DS_6631_056
8 Rev 1
1.4 Analog Front-End (AFE)
The AFE functions as a data acquisition system, controlled by the MPU. The main blocks in the AFE
consist of an input multiplexer, a delta-sigma A/D converter, a FIR decimation filter and a voltage
reference. The metrology input signals (IAP, IAN, IBP, IBN, ICP, ICN, VA, VB, VC, and TEMP) are
multiplexed before being sampled by the ADC. The ADC output is decimated by the FIR filter and the
results are stored in RAM where they can be accessed by the CE and the MPU.
The functionality of the AFE is established for various system requirements with different CE code. AFE
programmability includes, but is not limited to:
• Input multiplexer settings
• Voltage supply and temperature monitor inputs
• ADC sampling rate
• FIR length/resolution
VA
VB
MUX
VREF
4.9152 MHz
VBIAS
CROSS
CK32
VREF
MUX
CTRL
VC
MUX
V3P3A
FIR
VBIAS
∆Σ ADC
CONVERTER
+
-
VREF
TEMP
V3P3D
FIR_DONE
FIR_START
IBP
IBN
ICP
ICN
IAP
IAN
-
+
-
+
-
+
Figure 2: AFE Block Diagram
1.4.1 Analog Current and Voltage Inputs
With all CE code implementations for the 78M6631, pins IAP, IAN, IBP, IBN, ICP, ICN, VA, VB, and VC
are analog inputs to the AFE for measuring current and voltage. Various current sensor technologies can
be supported including Current Transformers, Resistive Shunts, and Rogowski coils.