ADE7758ARWZ Analog Devices Inc, ADE7758ARWZ Datasheet - Page 22

• Manufacturer Part Number: ADE7758ARWZ
• Description: IC ENERGY METERING 3PHASE 24SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARWZ

• Input Impedance: 380 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 8mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Meter Type: 3 Phase
• Ic Function: Poly Phase Multifunction Energy Metering IC
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: SOIC
• No. Of Pins: 24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADE7758
VOLTAGE CHANNEL ADC
Figure 49 shows the ADC and signal processing chain for the
input VA in the voltage channel. The VB and VC channels have
similar processing chains.
For active and reactive energy measurements, the output of the
ADC passes to the multipliers directly and is not filtered. This
solution avoids the much larger multibit multiplier and does not
affect the accuracy of the measurement. An HPF is not
implemented on the voltage channel to remove the dc offset
because the HPF on the current channel alone should be
sufficient to eliminate error due to ADC offsets in the power
calculation. However, ADC offset in the voltage channels
produces large errors in the voltage rms calculation and affects
the accuracy of the apparent energy calculation.
Voltage Channel Sampling
The waveform samples on the voltage channels can also be
routed to the WFORM register. However, before passing to the
WFORM register, the ADC outputs pass through a single-pole,
low-pass filter (LPF1) with a cutoff frequency at 260 Hz.
Figure 50 shows the magnitude and phase response of LPF1.
This filter attenuates the signal slightly. For example, if the line
frequency is 60 Hz, the signal at the output of LPF1 is
attenuated by 3.575%. The waveform samples are 16-bit, twos
complement data ranging between 0x2748 (+10,056d) and
0xD8B8 (−10,056d). The data is sign extended to 24-bit in the
WFORM register.
H
( )
f
=
1
+
⎛
⎜
⎜
⎝
260
60
1
Hz
Hz
⎞
⎟
⎟
⎠
VA
2
VAP
VN
=
0V
VA
. 0
974
ANALOG INPUT
RANGE
+
PGA
–
GAIN[6:5]
×1, ×2, ×4
=
−
. 0
225
Figure 49. ADC and Signal Processing in Voltage Channel
GAIN
0.5V
dB
ADC
0xD7AE
0x2852
0x0
Rev. D | Page 22 of 72
(3)
CALIBRATION
f
PHCAL[6:0]
3dB
PHASE
LPF1
Φ
= 260Hz
Note that LPF1 does not affect the active and reactive energy
calculation because it is only used in the waveform sampling
signal path. However, waveform samples are used for the
voltage rms calculation and the subsequent apparent energy
accumulation.
The WAVSEL[2:0] bits in the WAVMODE register should be
set to 001 (binary) to start the voltage waveform sampling. The
PHSEL[1:0] bits control the phase from which the samples are
routed. In waveform sampling mode, one of four output sample
rates can be chosen by changing Bit 5 and Bit 6 of the
WAVMODE register (see Table 20). The available output sample
rates are 26.0 kSPS, 13.5 kSPS, 6.5 kSPS, or 3.3 kSPS. By setting
the WFSM bit in the interrupt mask register to Logic 1, the
interrupt request output IRQ goes active low when a sample is
available. The 24-bit waveform samples are transferred from the
ADE7758 one byte (8 bits) at a time, with the most significant
byte shifted out first.
–20
–40
–60
–80
0
10
Figure 50. Magnitude and Phase Response of LPF1
50Hz
60Hz
0xD8B8
0xD869
0x2797
0x2748
TO ACTIVE AND
REACTIVE ENERGY
CALCULATION
TO VOLTAGE RMS
CALCULATION AND
WAVEFORM SAMPLING
0x0
0x0
LPF OUTPUT
WORD RANGE
LPF OUTPUT
WORD RANGE
FREQUENCY (Hz)
(60Hz; –13°)
100
(60Hz; –0.2dB)
1k
0
–10
–20
–30
–40