ade7880 Analog Devices, Inc., ade7880 Datasheet - Page 27

• Manufacturer Part Number: ade7880
• Description: Polyphase Multifunction Energy Metering Ic With Harmonic Monitoring
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
initialized with 0xFFF8000. DICOEFF is not used when the
integrator is turned off and can remain at 0x000000 in that case.
As stated in the Current Waveform Gain Registers section, the
serial ports of the ADE7880 work on 32-, 16-, or 8-bit words.
Similar to the registers shown in Figure 18, the DICOEFF 24-bit
signed register is accessed as a 32-bit register with four MSBs
Voltage Waveform Gain Registers
There is a multiplier in the signal path of each phase voltage.
The voltage waveform can be changed by ±100% by writing
a corresponding twos complement number to the 24-bit signed
current waveform gain registers (AVGAIN, BVGAIN, and
CVGAIN). For example, if 0x400000 is written to those registers,
the ADC output is scaled up by 50%. To scale the input by −50%,
write 0xC00000 to the registers. Equation 4 describes mathe-
matically the function of the current waveform gain registers.
–89.96
–89.97
–89.98
–89.99
–15
–20
–25
–30
Figure 22. Combined Gain and Phase Response of the
30
30
35
35
Digital Integrator (40 Hz to 70 Hz)
40
40
+0.5V/GAIN
-0.5V/GAIN
V
FREQUENCY (Hz)
FREQUENCY (Hz)
45
45
IN
0V
VAP
VN
V
IN
ANALOG INPUT RANGE
50
50
x1, x2, x4,x8,
PGA3
PGA3 bits
GAIN[8:6]
x16
55
55
60
60
REFERENCE
65
65
ADC
Figure 23. Voltage Channel Datapath
0xAEB86F=
0x514791=
-5,326,737
5,326,737
70
70
Rev. PrE | Page 27 of 103
0V
AVGAIN[23:0]
DSP
ADC OUTPUT RANGE
VOLTAGE CHANNEL
DATA RANGE
CONFIG3[0]
HPFEN bit
HPF
padded with 0s and sign extended to 28 bits, which practically
means it is transmitted equal to 0x0FFF8000.
When the digital integrator is switched off, the ADE7880 can
be used directly with a conventional current sensor, such as
a current transformer (CT).
VOLTAGE CHANNEL ADC
Figure 23 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 23 shows a full-scale voltage signal being applied to the
differential inputs (VA and VN). The ADC output swings
between −5,326,737 (0xAEB86F) and +5,326,737 (0x514791).
Note these are nominal values and every ADE7880 varies
around these values.
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 voltage rms calculation. In addition, waveform samples are
scaled accordingly.
As stated in the Current Waveform Gain Registers section, the
serial ports of the ADE7880 work on 32-, 16-, or 8-bit words,
and the DSP works on 28 bits. As presented in Figure 18, the
Voltage Waveform =
ADC
Output
0xAEB86F=
0x514791=
OVERVOLTAGE, SAG
ACTIVE AND REACTIVE
-5,326,737
VOLTAGE RMS (VRMS)
TOTAL/FUNDAMENTAL
POWER CALCULATION
5,326,737
LPF1
SAMPLE REGISTER
VOLTAGE PEAK,
VAWV WAVEFORM
CALCULATION
×
DETECT
0V

 

1
+
ZX SIGNAL
DATA RANGE
ZX DETECTION
Content
of
Voltage
2
23
Gain
Register
ADE7880

 

(4)