71M6521BE Datasheet, PDF (60/97 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6521BE
Energy Meter IC
DATA SHEET
JANUARY 2008
APPLICATION INFORMATION
Connection of Sensors (CT, Resistive Shunt)
Figure 28 and Figure 29 show how resistive dividers, current transformers, and restive shunts are connected to the voltage and
current inputs of the 71M6521BE.
VA = Vin * R_out/(R_out + R_in)
VA
V_in
R_in
R_out
core
Vout = R * I_out = R * I_in/N
I_in
I_out
IA ^Iin
R
V_out
V3P3
1/N
Filter
I_out
Figure 28: Resistive Voltage Divider (Left), Current Transformer (Right)
Vout = R * I_in
I_in
IA
R
V_out
V3P3
I_in
Figure 29: Resistive Shunt
Connecting 5V Devices
All digital input pins of the 71M6521BE are compatible with external 5V devices. I/O pins configured as inputs do not require
current-limiting resistors when they are connected to external 5V devices.
See the cautionary note on the restrictions for combined SEG/DIO pins configured as digital inputs in the Digital I/O
Section.
Page: 60 of 97
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