Cirrus Logic AN365 - Manual (Page 3)

AN365
AN365REV1 3
3.1 Connection Between a Rogowski Coil and the CS5480
Since the Rogowski coil has an inherent 20dB/decade gain, a single-pole low-pass RC anti-aliasing filter is not
capable of attenuating the high-frequency noise. Two cascaded low-pass RC filters are required to produce a
40dB/decade attenuation at high frequency. Figure 3 illustrates the typical connections between a Rogowski
coil sensor and the CS5480. If the Rogowski coil has a shielding lead, it should be connected to ground.
10
0
10
1
10
2
10
3
-90
-80
-70
-60
-50
-40
-30
Frequency (Hz)
P
has
e (
de
gr
ees
)
Phase of Rogowski Integrator
10
0
10
1
10
2
10
3
0
10
20
30
40
50
60
Frequency (Hz)
M
agni
tude (
dB
)
Magnitude of Rogowski Integrator
Figure 2. Frequency Response of the Digital Integrator
CS5480
IIN 1-
IIN 1+
27nF
27nF
27nF
27nF
V+
V-
GND GND
IIN1-
IIN1+
J1
Rogowski Coil
PA3202 NL
Current
1kΩ 100Ω
1kΩ 100Ω
Figure 3. Typical Connections Between a Rogowski Coil and the CS5480