ADE7758ARWZ Analog Devices Inc, ADE7758ARWZ Datasheet - Page 53

• 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

Power Offset Calibration Using Line Accumulation
Power offset calibration should be used for outstanding
performance over a wide dynamic range (1000:1). Calibration
of the power offset is done at or close to the minimum current.
The ADE7758 has power offset registers for watts and VAR,
xWATTOS (0x39 to 0x3B) and xVAROS (0x3C to 0x3E). Offsets in
the VA measurement are compensated by adjusting the rms offset
registers (see the Calibration of IRMS and VRMS Offset section).
More line cycles could be required at the minimum current to
minimize the effect of quantization error on the offset
calibration. For example, if a current of 40 mA results in an
active energy accumulation of 113 after 2000 half line cycles,
one LSB variation in this reading represents an 0.8% error. This
measurement does not provide enough resolution to calibrate
out a <1% offset error. However, if the active energy is
accumulated over 37,500 half line cycles, one LSB variation
results in 0.05% error, reducing the quantization error.
Figure 83 shows the steps to calibrate the power offsets using
the line accumulation mode.
Step 1: If the values change after gain calibration, Step 1, Step 3,
and Step 4 from the gain calibration should be repeated to
configure the LCYCMODE, LINECYC, and MASK registers.
Select Phase A, Phase B, or Phase C for a line period measure-
ment with the FREQSEL[1:0] bits in the MMODE register (0x14).
For example, clearing Bit 1 and Bit 0 selects Phase A for line
period measurement.
Step 2: Set the test system for I
Step 3: Reset the interrupt status register by reading RSTATUS
(0x1A).
Step 4: Read all xWATTHR energy registers (0x01 to 0x03) after
the LENERGY interrupt and store the values.
Step 4a: If it is not known, the line period is available in the
ADE7758’s frequency register, FREQ (0x10). To configure line
period measurement, select the phase for period measurement
in the MMODE[1:0] and set LCYCMODE[7].
Step 5: Calculate the value to be written to the xWATTOS
registers according to the following equations:
Offset
xWATTOS
xWATTHR
=
I
[
MIN
11
0 :
×
]
I
=
TEST
AccumTime
–
⎛
⎜
⎜
⎝
xWATTHR
Offset
I
MIN
MIN
–
×
×
, V
I
TEST
4
CLKIN
NOM
I
TEST
, and unity power factor.
×
LINECYC
LINECYC
×
2
29
ITEST
IMIN
⎞
⎟
⎟
⎠
×
I
(73)
(74)
Rev. D | Page 53 of 72
MIN
where:
AccumTime is defined in Equation 58.
LINECYC
LINECYC
Step 6: Write to all xWATTOS registers (0x39 to 0x3B).
Step 7: Set the test system for I
inductive to calibrate VAR gain.
Step 8: Repeat Steps 3, 4, and 5.
Step 9: Calculate the value written to the xVAROS registers
according to the following equations:
where the FREQ[11:0] register is configured for line period
readings.
Example:
This example only shows Phase A of the phase active power
offset calibration. Both active and reactive power offset for
all phases can be calibrated simultaneously using the method
explained in the Power Offset Calibration Using Line
Accumulation section.
For this example, I
V
Power Factor = 1, Frequency = 50 Hz, and CLKIN = 10 MHz.
Also, LINECYC
After accumulat
I
AWATTHR (0x01) register. At I
AWATTHR register. By using Equation 73, this is equivalent to
0.161 LSBs of offset; therefore, using Equation 61 and Equation 74,
the value written to AWATTOS is 0d.
Offset
xWATTHR
xWATTHR
xVAROS
xVARHR
TEST
FULLSCALE
, the example ADE7758 meter shows 14804d in the
Offset
592
=
[11
×
IMIN
IMAX
I
= 500 V, I
Power Offset Calibration Using Line Accumulation
MIN
=
10
I
I
TEST
MIN
:
0]
is the number of line cycles accumulated at I
×
is the number of line cycles accumulated at I
–
ITEST
=
ing
I
⎛
⎜
⎝
is the value in the energy register at I
is the value in the energy register at I
TEST
14804
AccumTime
MIN
0.05
FULLSCALE
over 0x800 line cycles fo
= 0x800 and LINECYC
–
= 50 mA,
⎛
⎜
⎜
⎝
–
×
Offset
xVARHR
10
0x4000
I
0x800
MIN
= 130 A, MC = 3200 impulses/k
MIN
×
×
–
MIN
I
4
CLKIN
TEST
I
, V
TEST
⎞
⎟
⎠
I
TEST
, the meter shows 592
×
NOM
= 10 A, V
0.05
×
, and zero power factor
LINECYC
LINECYC
×
FREQ
=
IMIN
r ga
0.16
NOM
202
= 0x4000.
in calibrat
[
11
ADE7758
ITEST
= 220 V,
IMIN
:
] 0
MIN
TEST
⎞
× ⎟ ⎟
⎠
×
d in the
.
2
.
ion at
MIN
26
MAX
I
Wh,
MIN
(75)
(76)
.
.