71M6545 Datasheet, PDF (71/134 Pages) Maxim Integrated Products – Four-Quadrant Metering, Phase Metrology Processors Flash/RAM Size

PDS_6545_009
Data Sheet 71M6545/H
4 APPLICATION INFORMATION
4.1 Connecting 5 V Devices
All digital input pins of the 71M6545/H 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 23 through Figure 26 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 71M6545/H. All input signals to the 71M6545/H sensor inputs are voltage signals providing a
scaled representation of either a sensed voltage or current.
The analog input pins of the 71M6545/H 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 23: Resistive Voltage Divider (Voltage Sensing)
I_IN
I_OUT
IADCn
(n = 0,1,...7)
CT
RBURDEN
VOUT
Noise Filter
V3P3A
1:N
Figure 24. 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 25: 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 26: Differential Resistive Shunt Connections (Current Sensing)
v1.0
© 2008–2011 Teridian Semiconductor Corporation
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