ade7854 Analog Devices, Inc., ade7854 Datasheet - Page 13

• Manufacturer Part Number: ade7854
• Description: Poly Phase Multifunction Energy Metering Ic With Neutral Current Measurement
• Manufacturer: Analog Devices, Inc.

Preliminary Technical Data
TERMINOLOGY
Measurement Error
The error associated with the energy measurement made by the
ADE7854 is defined by
Phase Error Between Channels
The high-pass filter (HPF) and digital integrator introduce a
slight phase mismatch between the current and the voltage
channel. The all-digital design ensures that the phase matching
between the current channels and voltage channels in all three
phases is within ±0.1° over a range of 45 Hz to 65 Hz and ±0.2°
over a range of 40 Hz to 1 kHz. This internal phase mismatch
can be combined with the external phase error (from current
sensor or component tolerance) and calibrated with the phase
calibration registers.
Power Supply Rejection (PSR)
This quantifies the ADE7854 measurement error as a
percentage of reading when the power supplies are varied. For
the ac PSR measurement, a reading at nominal supplies (3.3 V)
is taken. A second reading is obtained with the same input
signal levels when an ac signal (TBD mV rms/TBD Hz) is
introduced onto the supplies. Any error introduced by this ac
signal is expressed as a percentage of reading—see the
Measurement Error definition.
For the dc PSR measurement, a reading at nominal supplies
(3.3 V) is taken. A second reading is obtained with the same
input signal levels when the power supplies are varied ±10%.
Any error introduced is again expressed as a percentage of the
reading.
ADC Offset Error
This refers to the dc offset associated with the analog inputs to
the ADCs. It means that with the analog inputs connected to
Measuremen
Energy
Registered
t
Error
by
=
True
ADE7
Energy
85
8
/
7854
–
True
Energy
×
100
%
Rev. PrC| Page 13 of 71
(1)
AGND that the ADCs still see a dc analog input signal. The
magnitude of the offset depends on the gain and input range
selection (see the Typical Performance Characteristics section).
However, the offset is removed from the current and voltage
channels by a HPF and the power calculation is not affected by
this offset.
Gain Error
The gain error in the ADCs of the ADE7854 is defined as the
difference between the measured ADC output code (minus the
offset) and the ideal output code (see the Current Channel ADC
section and the Voltage Channel ADC section). The difference
is expressed as a percentage of the ideal code.
Gain Error Match
The gain error match is defined as the gain error (minus the
offset) obtained when switching between a gain of 1, 2, 4, 8 or
16. It is expressed as a percentage of the output ADC code
obtained under a gain of 1.
CF Jitter
The period of pulses at one of CF1, CF2 or CF3 pins is
continuously measured. The maximum, minimum and average
values of 4 consecutive pulses are computed:
CF
MAX =
MIN =
The CF jitter is then computed as
AVG
jitter
=
min(
=
max(
Period
MAX
Period
Period
AVG
0
−
+
MIN
Period
0
0
,
Period
,
Period
⋅
100
1
+
4
[%]
1
Period
1
,
Period
,
Period
2
2
+
2
,
Period
,
Period
Period
3
3
3
)
)
ADE7854