Datasheet

71M6543F/71M6543G Data Sheet
v2 85
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 Demo Boards must not
be used. Refer to the Demo Board schematics for complete sensor input circuits and
corresponding component values.
V
IN
R
OUT
V3P3A
VADCn
(n = 8, 9 or 10)
Figure 27: Resistive Voltage Divider (Voltage Sensing)
I
IN
IADCn
V3P3A
V
OUT
I
OUT
R
BURDEN
CT
1:N
Noise Filter
(n = 0,1,...7)
Figure 28. CT with Single-Ended Input Connection (Current Sensing)
I
IN
IADCn
IADCn+1
V3P3A
V
OUT
I
OUT
R
BURDEN
CT
1:N
Bias Network and Noise Filter
(n = 0, 2, 4 or 6)
Figure 29: CT with Differential Input Connection (Current Sensing)
I
IN
R
SHUNT
IADCn
IADCn+1
V3P3A
V
OUT
Bias Network and Noise Filter
(n = 2, 4 or 6)
Figure 30: Differential Resistive Shunt Connections (Current Sensing)