ADE7753ARS Analog Devices Inc, ADE7753ARS Datasheet - Page 25

• Manufacturer Part Number: ADE7753ARS
• Description: IC ENERGY METERING DETEC 20-SSOP
• Manufacturer: Analog Devices Inc

Specifications of ADE7753ARS

• Rohs Status: RoHS non-compliant
• Input Impedance: 390 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 3mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP (0.200", 5.30mm Width)
• Meter Type: Single Phase
• For Use With: EVAL-ADE7753ZEB - BOARD EVALUATION AD7753

Channel 2 has only one analog input range (0.5 V differential).
Like Channel 1, Channel 2 has a PGA with gain selections of 1,
2, 4, 8, and 16. For energy measurement, the output of the ADC
is passed directly to the multiplier and is not filtered. An HPF is
not required to remove any dc offset since it is only required to
remove the offset from one channel to eliminate errors due to
offsets in the power calculation. When in waveform sampling
mode, one of four output sample rates can be chosen by using
Bits 11 and 12 of the mode register. The available output sample
rates are 27.9 kSPS, 14 kSPS, 7 kSPS, or 3.5 kSPS—see the Mode
Register (0x09) section. The interrupt request output IRQ
signals that a sample is available by going active low. The timing
is the same as that for Channel 1, as shown in Figure 52.
Channel 2 RMS Calculation
Figure 56 shows the details of the signal processing chain for
the rms calculation on Channel 2. The Channel 2 rms value is
processed from the samples used in the Channel 2 waveform
sampling mode. The rms value is slightly attenuated because of
LPF1. Channel 2 rms value is stored in the unsigned 24-bit
VRMS register. The update rate of the Channel 2 rms
measurement is CLKIN/4.
With the specified full-scale ac analog input signal of 0.5 V, the
output from the LPF1 swings between 0x2518 and 0xDAE8 at
60 Hz—see the Channel 2 ADC section. The equivalent rms
value of this full-scale ac signal is approximately 1,561,400
(0z17D338) in the VRMS register. The voltage rms measure-
ment provided in the ADE7753 is accurate to within ±0.5% for
signal input between full scale and full scale/20. The conversion
CHANNEL 2
ANALOG
INPUT RANGE
0.5V, 0.25, 0.125,
62.5mV, 31.25mV
V2
V2P
V2N
0V
LPF1
V1
×1, ×2, ×4,
×8, ×16
PGA2
Figure 55. ADC and Signal Processing in Channel 2
VOLTAGE SIGNAL (V(t))
0xDAE8
0x2518
{GAIN [7:5]}
Figure 56. Channel 2 RMS Signal Processing
0x0
REFERENCE
Rev. A | Page 25 of 60
ADC 2
2.42V
0xDAE8
0xD7AE
0x2581
0x2852
0x0000
LPF3
WORD RANGE
LPF OUTPUT
from the register value to volts must be done externally in the
microprocessor using a volts/LSB constant. Since the low-pass
filtering used for calculating the rms value is imperfect, there is
some ripple noise from 2 ω term present in the rms measure-
ment. To minimize the noise effect in the reading, synchronize
the rms reading with the zero crossings of the voltage input.
Channel 2 RMS Offset Compensation
The ADE7753 incorporates a Channel 2 rms offset compensation
register (VRMSOS). This is a 12-bit signed register that can be
used to remove offset in the Channel 2 rms calculation. An
offset could exist in the rms calculation due to input noises and
dc offset in the input samples. The offset calibration allows the
contents of the VRMS register to be maintained at 0 when no
voltage is applied. One LSB of the Channel 2 rms offset is
equivalent to one LSB of the rms register. Assuming that the
maximum value from the Channel 2 rms calculation is
1,561,400d with full-scale ac inputs, then one LSB of the
Channel 2 rms offset represents 0.064% of measurement
error at –60 dB down of full scale.
where VRMS
The voltage rms offset compensation should be done by testing
the rms results at two non-zero input levels. One measurement
can be done close to full scale and the other at approximately
full scale/10. The voltage offset compensation can be derived
from these measurements. If the voltage rms offset register does
not have enough range, the CH2OS register can also be used.
LPF1
sgn
VRMS = VRMS
VRMOS[11:0]
2
9
2
8
+
0
is the rms measurement without offset correction.
2
ACTIVE AND REACTIVE
ENERGY CALCULATION
VRMS CALCULATION
AND WAVEFORM
SAMPLING
(PEAK/SAG/ZX)
2
+
2
1
0x17D338
2
0
0
+ VRMSOS
0x00
VRMS[23:0]
02875-0-054
02875-0-0055
ADE7753
(6)