71M6541D Datasheet, PDF (92/166 Pages) Maxim Integrated Products – 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs

71M6541D/F/G and 71M6542F/G Data Sheet
4 Application Information
4.1 Connecting 5 V Devices
All digital input pins of the 71M654x 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 Direct Connection of Sensors
Figure 31 through Figure 34 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 71M654x. All input signals to the 71M654x sensor inputs are voltage signals providing a scaled
representation of either a sensed voltage or current.
The analog input pins of the 71M654x 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.
RIN
VA
VIN
ROUT
V3P3A
Figure 31: Resistive Voltage Divider (Voltage Sensing)
IIN
IOUT
IAP
CT
RBURDEN
VOUT
Noise Filter
V3P3A
1:N
Figure 32. CT with Single-Ended Input Connection (Current Sensing)
I_IN
I_OUT
IAP
CT
RBURDEN
VOUT
V3P3A
IAN
Bias Network and Noise Filter
1:N
Figure 33: CT with Differential Input Connection (Current Sensing)
IIN
IAP
RSHUNT
VOUT
V3P3A
IAN
Bias Network and Noise Filter
Figure 34: Differential Resistive Shunt Connections (Current Sensing)