EVAL-ADE7759E Ver la hoja de datos (PDF) - Analog Devices
Número de pieza
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EVAL-ADE7759E Datasheet PDF : 32 Pages
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30
20
10
0
–10
–20
–30
–40
–50
–60
101
102
103
104
FREQUENCY – Hz
Figure 10. Gain Response of the Digital Integrator
–88.0
–88.5
–89.0
–89.5
–90.0
–90.5
–91.0
–91.5
–92.0
101
102
103
104
FREQUENCY – Hz
Figure 11. Phase Response of the Digital Integrator
0
–1
–2
–3
–4
–5
–6
40
45
50
55
60
65
70
FREQUENCY – Hz
Figure 12. Gain Response of the Digital Integrator
(40 Hz to 70 Hz)
ADE7759
–89.980
–89.985
–89.990
–89.995
–90.000
–90.005
–90.010
–90.015
–90.020
40
45
50
55
60
65
70
FREQUENCY – Hz
Figure 13. Phase Response of the Digital Integrator
(40 Hz to 70 Hz)
Note that the integrator has a –20 dB/dec attenuation and approxi-
mately –90° phase shift. When combined with a di/dt sensor, the
resulting magnitude and phase response should be a flat gain
over the frequency band of interest. However, the di/dt sensor has
a 20 dB/dec gain associated with it, and generates significant high
frequency noise. A more effective antialiasing filter is needed to
avoid noise due to aliasing—see Antialias Filter section.
When the digital integrator is switched off, the ADE7759 can be
used directly with a conventional current sensor such as current
transformer (CT) or a low resistance current shunt.
ZERO CROSSING DETECTION
The ADE7759 has a zero crossing detection circuit on Channel 2.
This zero crossing is used to produce an external zero cross
signal (ZX) and it is also used in the calibration mode—see
Energy Calibration section. The zero crossing signal is also used
to initiate a temperature measurement on the ADE7759—see
Temperature Measurement section. Figure 14 shows how the
zero cross signal is generated from the output of LPF1.
V2P
V2
V2N
؋1, ؋2, ؋4,
؋8, ؋16
REFERENCE
{GAIN [7:5]}
PGA2
1
ADC 2
–63% TO +63% FS
TO
MULTIPLIER
ZERO
CROSS
ZX
LPF1
f–3dB = 156Hz
21.04؇ @ 60Hz
1.0
0.93
ZX
V2
LPF1
Figure 14. Zero Cross Detection on Channel 2
REV. 0
–13–
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