Powering Up The Evaluation Kit Boards; Analog Inputs - Analog Devices EVAL-ADE7903EBZ User Manual

UG-797

POWERING UP THE EVALUATION KIT BOARDS

The interface board receives power via the USB cable connected
to the PC. A 3.3 V regulator then powers the SDP-B board
microcontroller and, across the isolation barrier, the
ADC populating the evaluation board. No additional power
source is required for the ADE7903

ANALOG INPUTS

Current and voltage signals are connected at the test pins placed
on the evaluation board. All analog input signals are filtered
using the on-board antialiasing filters before the signals are
connected to the ADE7903 ADC. The components used on the
board are the values recommended for use with the ADE7903.
Current Sense Inputs (IP_IN and IM_IN Test Pins)
The ADE7903 measures the voltage across a shunt at its IP and
IM pins. Figure 4 shows the structure used for the current
input.
E1
R8 R15
0Ω 1kΩ
IP_IN
E2
GND
AGND_ADC
E3
R9 R16
0Ω 1kΩ
IM_IN
Figure 4. Current Input Structure on the Evaluation Board
R8, R9, R20, and R21 are 0 Ω resistors that do not need to be
implemented on a real meter board. R15/C12 and R16/C15
RC networks are the antialiasing filters. The default corner
frequency of these low-pass filters is 4.8 kHz (1 kΩ/33 nF).
These filters can easily be adjusted by replacing the components
on the evaluation board.
The E1, E2, and E3 ferrite beads filter the high frequency noise
that may be induced into the wires.
ADE7903
evaluation kit boards.
ADE7903
R20
0Ω
IP
C12
33nF
D3 D6
C15
33nF
R21
0Ω
IM
The absolute maximum voltage on the IP and IM pins of the
ADE7903 is ±2 V. The D3 and D6 diodes protect the IP and IM
pins against voltages greater than ±1 V. The maximum signal level
permissible at the IP pin of the
The signal range must not exceed ±0.03125 V, with respect to
AGND_ADC, for specified operation.
The shunt is connected between the IP_IN and IM_IN test pins.
The shunt maximum value is a function of the maximum
current to be measured on every phase:
×
31 . 25
=
R
where:
×
31 . 25 10
2
is the rms value of the full-scale voltage accepted at the ADC input.
I is the maximum current to be measured. It is called the full-
FS
scale current.
Figure 5 shows how a shunt is connected to the current input
structure. The shunt is connected between the P1 and P1'
energy meter line inputs. The IP_IN and IM_IN test pins are
connected to the shunt measurement poles, while GND, the test
pin that is the ground of the ADE7903, is connected to the
ground pole of the shunt.
TO P1'
METER
INPUT
TO P1
METER
INPUT
Figure 5. Example of a Shunt Connection
Rev. 0 | Page 4 of 12
EVAL-ADE7903EBZ User Guide
ADE7903 is ±0.03125 V peak.
−
3
10
1
×
2 I
FS
3 −
E1
R8 R15
0Ω 1kΩ
IP_IN
C12
33nF
E2
GND
AGND_ADC
C15
E3
33nF
R9 R16
0Ω 1kΩ
IM_IN
ADE7903
R20
0Ω
IP
D3 D6
R21
0Ω
IM