ADE7854AACPZ View Datasheet(PDF) - Analog Devices
Part Name
Description
MFG CO.
'ADE7854AACPZ' PDF : 96 Pages View PDF
Data Sheet
ADE7854A/ADE7858A/ADE7868A/ADE7878A
The digital integrator algorithm uses the DICOEFF 24-bit
signed register. At power-up or after a reset, its value is 0x000000.
Before turning on the integrator, it is necessary to initialize this
register with 0xFFF8000. When the integrator is turned off,
DICOEFF is not used and can remain at 0x000000.
–15
–20
–25
–30
30
35
40
45
50
55
60
65
70
FREQUENCY (Hz)
–89.96
–89.97
–89.98
–89.99
30
35
40
45
50
55
60
65
70
FREQUENCY (Hz)
Figure 41. 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 device work on 32-, 16-, or 8-bit words. Similar to
the registers shown in Figure 34, the DICOEFF 24-bit signed regis-
ter is accessed as a 32-bit register with four MSBs padded with
0s; thus, the 24-bit word is sign extended to 28 bits, meaning
that it is practically transmitted equal to 0xFFF8000.
When the digital integrator is switched off, the ADE7854A/
ADE7858A/ADE7868A/ADE7878A can be used directly with a
conventional current sensor, such as a current transformer (CT).
VOLTAGE CHANNEL ADC
Figure 42 shows the ADC and signal processing chain for the
VA voltage channel. The VB and VC voltage 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 peak, the
ADC produces its maximum output code value. Figure 42
shows a full-scale voltage signal applied to the differential inputs
(VAx and VN); the ADC output swings between −5,928,256
(0xA58AC0) and +5,928,256 (0x5A7540).
Voltage Waveform Gain Registers
There is a multiplier in the signal path of each phase voltage. To
change the voltage waveform by ±100%, write a corresponding
twos complement number to the 24-bit signed voltage waveform
gain registers (AVGAIN, BVGAIN, and CVGAIN). For example,
writing 0x400000 to those registers scales up the ADC output by
50%. To scale the input by −50%, write 0xC00000 to the registers.
Equation 4 describes the function of the current waveform gain
registers.
Voltage Waveform =
Contents of Voltage Gain Register
ADC Output 1
223
(4)
Changing the content of the AVGAIN, BVGAIN, and CVGAIN
registers affects all calculations based on its voltage; that is, it affects
the corresponding phase active/reactive/apparent energy and volt-
age rms calculation, and waveform samples are scaled accordingly.
As stated in the Current Waveform Gain Registers section, the
serial ports of the device work on 32-, 16-, or 8-bit words, and
the DSP works on 28 bits. As shown in Figure 34, the AVGAIN,
BVGAIN, and CVGAIN registers are accessed as 32-bit registers
with four MSBs padded with 0s and sign extended to 28 bits.
VOLTAGE PEAK,
OVERVOLTAGE,
SAG DETECT
VAP
VIN
VN
PGA3 BITS
GAIN[8:6]
×1, ×2, ×4, ×8, ×16
PGA3
REFERENCE
DSP
HPFDIS
[23:0] AVGAIN[23:0]
ADC
HPF
CURRENT RMS (VRMS)
CALCULATION
VAWV WAVEFORM
SAMPLE REGISTER
TOTAL/FUNDAMENTAL
ACTIVE AND REACTIVE
POWER CALCULATION
VIN
+0.5V/GAIN
0V
0x5A7540 =
+5,928,256
VOLTAGE CHANNEL
DATA RANGE
0V
LPF1
ZX DETECTION
0x5A7540 =
+5,928,256
ZX SIGNAL
DATA RANGE
–0.5V/GAIN
0xA58AC0 =
–5,928,256
0V
ANALOG INPUT RANGE
ANALOG OUTPUT RANGE
Figure 42. Voltage Channel Datapath
0xA58AC0 =
–5,928,256
Rev. C | Page 31 of 96
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