ADE7758ARWZRL Analog Devices Inc, ADE7758ARWZRL Datasheet - Page 54

• Manufacturer Part Number: ADE7758ARWZRL
• Description: IC,Power Metering,SOP,24PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARWZRL

• 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: Lead free / RoHS Compliant

ADE7758
Calibration of IRMS and VRMS Offset
IRMSOS and VRMSOS are used to cancel
contributions from the inputs. The calibration method is th
same whether calibrating using the pulse outputs or line
accumulation. Reading the registers is required for this
calibration because there is no rms pulse output. The rms o
calibration should be performed before VAGAIN calibration.
The rms offset calibration also removes offset from the VA
calculation. For this reason, no VA offset register exists in the
ADE7758.
AccumTime
AWATTOS
STEP 5
WRITE TO
xVRMSOS
xIRMSOS
YES
=
=
54.64
STEP 1
STEP 2
2
CONFIGURATION
ZERO CROSSING
ZERO CROSSING
REGISTERS FOR
ON ALL PHASES
ON ALL PHASES
SET INTERRUPT
×
0.161
MASK FOR
PHASES?
2085
TESTED
START
×
ALL
SET
10
0
SYSTEM FOR
×
×
×
I
TEST
9
MHz
4000
4
SET UP
1
6 .
, V
×
NOM
10
NO
×
1
−
2
FOR I
6
STEP 4
29
SET UP SYSTEM
×
V
CONDITIONS?
REGISTERS
FULLSCALE
READ RMS
=
noise and offset
3
FULLSCALE
TESTED
−
=
ALL
0.088
5
2
. 4
STEP 3
64
/20
/500,
s
=
Figure 84. RMS Calibration Routine
0
ffset
e
Rev. D | Page 54 of 72
STEP 4D
The low-pass filter used to obtain the rms measurements is not
ideal; therefore, it is recommended to synchronize the readings
with the zero crossings of the voltage waveform and to average a
few measurements when reading the rms registers.
The ADE7758 IRMS measurement is linear over a 500:1 range,
and the VRMS measurement is linear over a 20:1 range. To
measure the voltage VRMS offset (xVRMSOS), measure rms
values at two different nonzero current levels, for example,
V
To measure the current rms offset (IRMSOS), measure rms
values at two different nonzero current levels, for example, I
and I
and V
a flowchart for calibrating the rms measurements.
NOM
xVRMS
xIRMS
READ
FULLSCALE
and V
NOM
YES
, and I
STEP 4B
RESET INTERRUPT
STATUS REGISTER
FULLSCALE
/500. This translates to two test conditions: I
INTERRUPT?
n = n + 1
FULLSCALE
/20.
STEP 4C
STEP 4A
NO
/500 and V
CHOOSE N
n = 0
NO
n = N?
FULLSCALE
YES
STEP 4E
CALCULATE THE
AVERAGE OF N
SAMPLES
/20. Figure 84 shows
END
TEST
TEST