71M6543F Datasheet, PDF (86/157 Pages) Maxim Integrated Products – Selectable Gain of 1 or 8 for One Current Energy Meter ICs Metrology Compensation

71M6543F/H and 71M6543G/GH Data Sheet
4 Application Information
4.1 Connecting 5 V Devices
All digital input pins of the 71M6543 are compatible with external 5 V devices. I/O pins configured as
inputs do not require current-limiting resistors when they are connected to external 5 V devices.
4.2 Directly Connected Sensors
Figure 27 through Figure 30 show voltage-sensing resistive dividers, current-sensing current transformers
(CTs) and current-sensing resistive shunts and how they are connected to the voltage and current inputs
of the 71M6543. All input signals to the 71M6543 sensor inputs are voltage signals providing a scaled
representation of either a sensed voltage or current.
The analog input pins of the 71M6543 are designed for sensors with low source impedance.
RC filters with resistance values higher than those implemented in the Teridian Demo Boards
must not be used. Please refer to the Demo Board schematics for complete sensor input
circuits and corresponding component values.
VADCn
(n = 8, 9 or 10)
VIN
ROUT
V3P3A
Figure 27: Resistive Voltage Divider (Voltage Sensing)
I_IN
I_OUT
IADCn
(n = 0,1,...7)
CT
RBURDEN
VOUT
Noise Filter
V3P3A
1:N
Figure 28. CT with Single-Ended Input Connection (Current Sensing)
IIN
IOUT
IADCn
(n = 0, 2, 4 or 6)
CT
RBURDEN
VOUT
V3P3A
IADCn+1
Bias Network and Noise Filter
1:N
Figure 29: CT with Differential Input Connection (Current Sensing)
IIN
RSHUNT
VOUT
V3P3A
IADCn
(n = 2, 4 or 6)
Bias Network and Noise Filter
IADCn+1
Figure 30: Differential Resistive Shunt Connections (Current Sensing)
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