Datasheet

ADE7854/ADE7858/ADE7868/ADE7878 Data Sheet
Rev. G | Page 32 of 100
–30
–
15
–20
–25
–89.96
–89.97
–89.98
–89.99
MAGNITUDE (dB)PHASE (Degrees)
30 35 40 45 50 55 60 65 70
FREQUENCY (Hz)
30 35 40 45 50 55 60 65 70
FREQUENCY (Hz)
0
8510-101
Figure 40. Combined Gain and Phase Response of the
Digital Integrator (40 Hz to 70 Hz)
As stated in the Current Waveform Gain Registers section, the
serial ports of the ADE7854/ADE7858/ADE7868/ADE7878 work
on 32-, 16-, or 8-bit words. Similar to the registers shown in Figure
35, the DICOEFF 24-bit signed register is accessed as a 32-bit
register with four MSBs padded with 0s and sign extended to 28
bits, which practically means it is transmitted equal to
0xFFF8000.
When the digital integrator is switched off, the ADE7854/
ADE7858/ ADE7868/ADE7878 can be used directly with a
conventional current sensor, such as a current transformer (CT).
VOLTAGE CHANNEL ADC
Figure 41 shows the ADC and signal processing chain for
Input VA in the voltage channel. The VB and VC channels
have similar processing chains. The ADC outputs are signed
twos complement 24-bit words and are available at a rate of
8 kSPS. With the specified full-scale analog input signal of
±0.5 V, the ADC produces its maximum output code value.
Figure 41 shows a full-scale voltage signal being applied to the
differential inputs (VA and VN). The ADC output swings
between −5,928,256 (0xA58AC0) and +5,928,256 (0x5A7540).
AVGAIN[23:0]
REFERENCE
HPFDIS
[23:0]
DSP
TOTAL/FUNDAMENTAL
ACTIVE AND REACTIVE
POWER CALCULATION
VO
LT
A
GE PEAK,
OVERVOLTAGE,
SAG DETECT
VAWV WAVEFORM
SAMPLE REGISTER
CURRENT RMS (VRMS)
CALCULATION
HPF
ADC
PGA3
VAP
ZX DETECTION
PGA3 BITS
GAIN[8:6]
×1, ×2, ×4, ×8, ×16
V
IN
V
IN
VN
ANALOG INPUT RANGE ANALOG OUTPUT RANGE
0x5A7540 =
+5,928,256
ZX SIGNAL
DATA RANGE
0V
0xA58AC0 =
–5,928,256
0x5A7540 =
+5,928,256
VOLTAGE CHANNEL
DATA RANGE
0V
0xA58AC0 =
–5,928,256
+0.5V/GAIN
–0.5V/GAIN
0V
LPF1
08510-025
Figure 41. Voltage Channel Datapath