AD7609BSTZ Analog Devices Inc, AD7609BSTZ Datasheet - Page 19

• Manufacturer Part Number: AD7609BSTZ
• Description: 58T8900
• Manufacturer: Analog Devices Inc

Specifications of AD7609BSTZ

• Resolution (bits): 18bit
• Sampling Rate: 250kSPS
• Input Channel Type: Differential
• Data Interface: Serial, SPI
• Supply Voltage Range - Analog: 4.75V To 5.25V
• Rohs Compliant: Yes

TERMINOLOGY
Integral Nonlinearity
The maximum deviation from a straight line passing through
the endpoints of the ADC transfer function. The endpoints of
the transfer function are zero scale, a ½ LSB below the first code
transition, and full scale at ½ LSB above the last code transition.
Differential Nonlinearity
The difference between the measured and the ideal 1 LSB
change between any two adjacent codes in the ADC.
Bipolar Zero Code Error
The deviation of the midscale transition (all 1s to all 0s) from
the ideal V
Bipolar Zero Code Error Match
The difference in bipolar zero code error between any two input
channels.
Positive Full-Scale Error
The last transition (from 011 . . . 10 to 011 . . . 11 in twos
complement coding) should occur for an analog voltage 1½
LSB below the nominal full scale (9.99977 V for the ±10 V
range and 4.99988 V for the ±5 V range). The positive full-scale
error is the deviation of the actual level of the last transition
from the ideal level.
Positive Full-Scale Error Match
The difference in positive full-scale error between any two input
channels.
Negative Full-Scale Error
The first transition (from 100 . . . 00 to 100 . . . 01 in twos
complement coding) should occur for an analog voltage ½ LSB
above the negative full scale (−9.999923 V for the ±10 V range
and −4.9999618 for the ±5 V range). The negative full-scale
error is the deviation of the actual level of the first transition
from the ideal level.
Negative Full-Scale Error Match
The difference in negative full-scale error between any two
input channels.
Track-and-Hold Acquisition Time
The track-and-hold amplifier returns to track mode at the end
of the conversion. The track-and-hold acquisition time is the
time required for the output of the track-and-hold amplifier to
reach its final value, within ±1 LSB, after the end of the conversion.
See the Track-and-Hold Amplifiers section for more details.
IN
voltage, that is, AGND.
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Signal-to-(Noise + Distortion) Ratio
The measured ratio of signal-to-(noise + distortion) at the
output of the ADC. The signal is the rms amplitude of the
fundamental. Noise is the sum of all nonfundamental signals
up to half the sampling frequency (f
depends on the number of quantization levels in the digitization
process: the more levels, the smaller the quantization noise. The
theoretical signal-to-(noise + distortion) ratio for an ideal N-bit
converter with a sine wave input is given by
Thus, for an 18-bit converter, this is 110.12 dB.
Total Harmonic Distortion (THD)
The ratio of the rms sum of the harmonics to the fundamental.
For the AD7609, it is defined as
where:
V
V
harmonics.
Peak Harmonic or Spurious Noise
The ratio of the rms value of the next largest component in the
ADC output spectrum (up to f
of the fundamental. Normally, the value of this specification is
determined by the largest harmonic in the spectrum, but for
ADCs where the harmonics are buried in the noise floor, it is
determined by a noise peak.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and fb,
any active device with nonlinearities creates distortion products
at sum and difference frequencies of mfa ± nfb, where m, n = 0,
1, 2, 3. Intermodulation distortion terms are those for which
neither m nor n is equal to 0. For example, the second-order
terms include (fa + fb) and (fa − fb), and the third-order terms
include (2fa + fb), (2fa − fb), (fa + 2fb), and (fa − 2fb).
The calculation of the intermodulation distortion is per the
THD specification, where it is the ratio of the rms sum of the
individual distortion products to the rms amplitude of the
sum of the fundamentals expressed in decibels (dB).
1
2
is the rms amplitude of the fundamental.
to V
Signal-to-(Noise + Distortion) = (6.02 N + 1.76) dB
THD (dB) =
20log
9
are the rms amplitudes of the second through ninth
V
2
2
+
V
3
2
+
V
4
2
+
S
V
/2, excluding dc) to the rms value
5
2
V
+
1
S
V
/2, excluding dc). The ratio
6
2
+
V
7
2
+
V
8
2
+
AD7609
V
9
2