71M6541F Maxim, 71M6541F Datasheet - Page 92

• Manufacturer Part Number: 71M6541F
• Description: The 71M6541D/71M6541F/71M6541G/71M6542F/71M6542G are Teridian™ 4th-generation single-phase metering SoCs with a 5MHz 8051-compatible MPU core, low-power RTC with digital temperature compensation, flash memory, and LCD driver
• Manufacturer: Maxim

71M6541D/F/G and 71M6542F/G Data Sheet
4
4.1
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
Figure 31
(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.
92
Application Information
Connecting 5 V Devices
Direct Connection of Sensors
through
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.
Figure 34: Differential Resistive Shunt Connections (Current Sensing)
Figure 32. CT with Single-Ended Input Connection (Current Sensing)
Figure 33: CT with Differential Input Connection (Current Sensing)
Figure 34
Figure 31: Resistive Voltage Divider (Voltage Sensing)
CT
I
IN
1:N
show voltage-sensing resistive dividers, current-sensing current transformers
CT
I
I
R
IN
IN
I
1:N
SHUNT
OUT
V
IN
R
V
I
BURDEN
OUT
OUT
R
Bias Network and Noise Filter
BURDEN
V
OUT
R
IN
V3P3A
Bias Network and Noise Filter
V
OUT
V3P3A
R
Noise Filter
OUT
V3P3A
VA
V3P3A
IAP
IAP
IAN
IAN
IAP
Rev 2