Datasheet

Data Sheet ADE9153A
Rev. 0 | Page 19 of 50
TERMINOLOGY
Crosstalk
Crosstalk is measured by grounding one channel and applying a
full-scale 50 Hz or 70 Hz signal on all the other channels. The
crosstalk is equal to the ratio between the grounded ADC output
value and its ADC full-scale output value. The ADC outputs
are acquired for 200 sec. Crosstalk is expressed in decibels.
Differential Input Impedance (DC)
The differential input impedance represents the impedance
between the IAP and IAN pair, the IBP and IBN pair, or the
VAP an d VA N p ai r.
ADC Offset
ADC offset is the difference between the average measured
ADC output code with both inputs connected to ground and
the ideal ADC output code of zero. ADC offset is expressed in mV.
ADC Offset Drift over Temperature
The ADC offset drift is the change in offset over temperature. It
is measured at −40°C, +25°C, and +85°C. Calculate the oset
drift over temperature as follows:



 






















C)25(C85
C25C85
,
C)25(C40
C25C40
max
OffsetOffset
OffsetOffset
Drift
Offset drift is expressed in μV/°C.
Channel Drift over Temperature
The channel drift over temperature coefficient includes the
temperature variation of the PGA and ADC gain when using
the internal voltage reference. This coefficient represents the overall
temperature coefficient of one channel. With the internal voltage
reference, the ADC gain is measured at −40°C, +25°C, and +85°C.
Then, the temperature coefficient is calculated as follows:


























C25C85C)25(
C25C85
,
C25C40C)25(
C25C40
max
Gain
GainGain
Gain
GainGain
Drift
Gain drift is measured in ppm/°C.
ADC Gain Error
The gain error in the ADCs represents the difference between the
measured ADC output code (minus the offset) and the ideal
output code when an external voltage reference of 1.25 V is used.
The difference is expressed as a percentage of the ideal code and
represents the overall gain error of one channel.
AC Power Supply Rejection (AC PSRR)
AC PSRR quantifies the measurement error as a percentage of
reading when the dc power supply is V
NOM
and modulated with
ac and the inputs are grounded. For the ac PSRR measurement,
100 sec of samples are captured with nominal supplies (3.3 V) and a
second set is captured with an additional ac signal (233 mV rms at
100 Hz) introduced onto the supplies. Then, the PSRR is
expressed as PSRR = 20 log
10
(V
RIPPLE
/V
NOMINAL
).
Signal-to-Noise Ratio (SNR)
SNR is calculated by inputting a 50 Hz signal, and acquiring
samples over 10 sec. The amplitudes for each frequency, up to
the bandwidth given in Table 1 as the ADC output bandwidth
(−3 dB), are calculated. To determine the SNR, the signal at 50 Hz
is compared to the sum of the power from all the other frequencies,
removing power from its harmonics. The value for SNR is
expressed in decibels.
ADC Output Pass Band
The ADC output pass band is the bandwidth within 0.1 dB,
resulting from the digital filtering in the sinc4 filter and sinc4
filter + infinite impulse response (IIR), low-pass filter (LPF).
ADC Output Bandwidth
The ADC output bandwidth is the bandwidth within −3 dB,
resulting from the digital filtering in the sinc4 and sinc4 + IIR LPF.
Speed of Convergence
The speed of convergence is the time it takes for mSure to
reach a certain level of accuracy. This speed, or time required, is
logarithmically proportional to the required accuracy. In other
words, if a greater accuracy is required in mSure autocalibration,
the time required increases logarithmically.
Similarly, the speed is related to the power mode in which
mSure is being run: the lower the power mode, the slower the
speed of convergence. This relationship is shown in Table 2 for
the specified system. The speed of convergence determines the
time it takes to complete the autocalibration process and to reach
a certain specified accuracy.
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