ADE7758ARW Analog Devices Inc, ADE7758ARW Datasheet - Page 45

• Manufacturer Part Number: ADE7758ARW
• Description: IC ENERGY METERING 24-SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARW

• Rohs Status: RoHS non-compliant
• 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
• Lead Free Status / RoHS Status: Not Compliant

Step 4: Set APCFNUM (0x45) and APCFDEN (0x46) to the
calculated value to perform a coarse adjustment on the
imp/kWh ratio. For VAR/VA calibration, set VARCFNUM
(0x47) and VARCFDEN (0x48) to the calculated value.
The pulse output frequency with one phase at full-scale inputs
is approximately 16 kHz. A sample set of meters could be tested
to find a more exact value of the pulse output at full scale in the
user application.
To calculate the values for APCFNUM/APCFDEN and
VARCFNUM/VARCFDEN, use the following formulas:
where:
MC is the meter constant.
I
V
V
which correspond to the full-scale ADC inputs of the ADE7758.
θ is the angle between the current and the voltage channel.
APCF
the test conditions.
APCFNUM is written to 0 or 1.
The equations for calculating the VARCFNUM and
VARCFDEN during VAR calibration are similar:
Because the APCFDEN and VARCFDEN values can be
calculated from the meter design, these values can be written
to the part automatically during production calibration.
Step 5: Set the test system for I
factor. For VAR calibration, the power factor should be set to 0
inductive in this step. For watt and VA, the unity power factor
should be used. VAGAIN can be calibrated at the same time as
WGAIN because VAGAIN can be calibrated at the unity power
factor, and both pulse outputs can be measured simultaneously.
However, when calibrating VAGAIN at the same time as WGAIN,
the rms offsets should be calibrated first (see the Calibration of
IRMS and VRMS Offset section).
Step 6: Measure the percent error in the pulse output, APCF
and/or VARCF, from the reference meter:
TEST
NOM
FULLSCALE
is the test current.
VARCF
APCF
APCF
APCFDEN
is the nominal voltage at which the meter is tested.
EXPECTED
and I
NOMINAL
EXPECTED
EXPECTED
is equivalent to the reference meter output under
FULLSCALE
=
=
INT
=
16
=
MC
are the values of current and voltage,
⎛
⎜
⎝
MC
kHz
APCF
1000
APCF
×
1000
×
I
×
TEST
V
I
×
TEST
EXPECTED
NOMINAL
TEST
FULLSCALE
3600
V
×
×
, V
NOM
3600
V
×
NOM
NOM
V
⎞
⎟
⎠
NOM
, and the unity power
×
×
cos
I
×
FULLSCALE
I
( )
TEST
sin
θ
( )
θ
(45)
(46)
(47)
(48)
Rev. D | Page 45 of 72
where CF
meter.
Step 7: Calculate xWG adjustment. One LSB change in xWG
(12 bits) changes the WATTHR register by 0.0244% and
therefore APCF by 0.0244%. The same relationship holds true
for VARCF.
When APCF is calibrated, the xWATTHR registers have the
same Wh/LSB from meter to meter if the meter constant and
the APCFNUM/APCFDEN ratio remain the same. The
Wh/LSB constant is
Return to Step 2 to calibrate Phase B and Phase C gain.
Example: Watt Gain Calibration of Phase A Using Pulse
Output
For this example, I
I
and Frequency = 50 Hz.
Clear APCFNUM (0x45) and write the calculated value to
APCFDEN (0x46) to perform a coarse adjustment on the
imp/kWh ratio, using Equation 45 through Equation 47.
With Phase A contributing to CF, at I
power factor, the example ADE7758 meter shows 2.058 Hz on
the pulse output. This is equivalent to a 5.26% error from the
reference meter value using Equation 49.
The AWG value is calculated to be −216 d using Equation 51,
which means the value 0xF28 should be written to AWG.
FULLSCALE
%
%Error
APCF
APCF
xWG =
APCF
APCF
APCFDEN
Wh
LSB
Error
= 130 A, MC = 3200 impulses/kWh, Power Factor = 1,
REF
=
EXPECTED
NOMINAL
NOMINAL
EXPECTED
= APCF
4
–
=
=
. 0
×
. 2
APCF
%
0244
058
= INT
Error
1000
MC
TEST
×
=
CF
=
=
. 1
EXPECTED
16
APCFNUM
Hz
APCFDEN
%
3200
–
REF
9556
= 10 A, V
1000
⎛
⎜
⎜
⎝
CF
×
kHz
. 1
–
542
. 1
REF
9556
APCFNUM
APCFDEN
×
Hz
9556
= the pulse output of the reference
×
×
10
1
×
3600
Hz
220
500
×
100
Hz
NOM
[
[
11
220
11
Hz
×
⎞
⎟
⎟
⎠
%
0 :
0 :
= 220 V, V
130
=
×
10
TEST
×
]
]
277
100
×
cos
×
, V
=
WDIV
⎛
⎜
⎝
1
%
( )
. 0
0
NOM
+
1
542
=
=
xWG
FULLSCALE
. 5
, and the unity
. 1
26
kHz
9556
ADE7758
2
%
[
12
11
0 :
Hz
= 500 V,
]
⎞
⎟
⎠
(49)
(50)
(51)
(52)