EVAL-ADE7816EBZ AD [Analog Devices], EVAL-ADE7816EBZ Datasheet - Page 19

• Manufacturer Part Number: EVAL-ADE7816EBZ
• Description: Six Current Channels, One Voltage Channel
• Manufacturer: AD [Analog Devices]

Data Sheet
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Antialiasing Filters
Each analog input pin requires that a simple RC filter be connected
to the input. The role of the RC filter is to prevent aliasing. The
aliasing effect is caused by frequency components (which are
higher than half the sampling rate of the ADC) folding back and
appearing in the sampled signal at a frequency that is below half
the sampling rate. Aliasing is an artifact of all sampled systems.
For conventional current sensors, it is recommended that one
RC filter with a corner frequency of 5 kHz be used for the
attenuation to be sufficiently high at the sampling frequency
of 1.024 MHz. The 20 dB per decade attenuation of this filter
is usually sufficient to eliminate the effects of aliasing for
conventional current sensors (see Figure 26).
PHASE
TRANSFORMER
CURRENT
Figure 26. Current Transformer Input Connections
RB
1kΩ
1kΩ
22nF
22nF
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However, a di/dt sensor, such as a Rogowski coil, has a 20 dB per
decade gain. This neutralizes the 20 dB per decade attenuation
produced by the low-pass filter (LPF). Therefore, when using a
di/dt sensor, a second pole is required. One simple approach is
to cascade one additional RC filter, thereby producing a −40 dB
per decade attenuation (see Figure 27).
LOAD
PHASE
ROGOWSKI
COIL
Figure 27. Rogowski Coil Input Connections
100Ω
100Ω
22nF
22nF
1kΩ
1kΩ
22nF
22nF
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