AD7898AR-10 Analog Devices Inc, AD7898AR-10 Datasheet - Page 6
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AD7898AR-10
Manufacturer Part Number
AD7898AR-10
Description
A/D Converter (A-D) IC
Manufacturer
Analog Devices Inc
Datasheet
1.AD7898ARZ-10REEL.pdf
(16 pages)
Specifications of AD7898AR-10
No. Of Bits
12 Bit
Mounting Type
Surface Mount
No. Of Channels
1
Interface Type
Serial
Package / Case
8-SOIC
Rohs Status
RoHS non-compliant
Number Of Bits
12
Sampling Rate (per Second)
220k
Data Interface
Serial
Number Of Converters
1
Power Dissipation (max)
22.5mW
Voltage Supply Source
Single Supply
Operating Temperature
-40°C ~ 85°C
Lead Free Status / RoHS Status
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Part Number:
AD7898AR-10
Manufacturer:
ADI/亚德诺
Quantity:
20 000
TERMINOLOGY
Signal to (Noise + Distortion) Ratio
This is the measured ratio of signal to (noise + distortion) at the
output of the A/D converter. The signal is the rms amplitude of
the fundamental. Noise is the rms sum of all nonfundamental
signals up to half the sampling frequency (f
The ratio is dependent upon the number of quantization levels
in the digitization process; the more levels, the smaller the quan-
tization noise. The theoretical signal to (noise + distortion) ratio
for an ideal N-bit converter with a sine wave input is given by:
Thus for a 12-bit converter, this is 74 dB.
Total Harmonic Distortion
Total harmonic distortion (THD) is the ratio of the rms sum of
harmonics to the fundamental. For the AD7898, it is defined as:
where V
V
sixth harmonics.
Peak Harmonic or Spurious Noise
Peak harmonic or spurious noise is defined as the ratio of the
rms value of the next largest component in the ADC output
spectrum (up to f
fundamental. Normally, the value of this specification is deter-
mined by the largest harmonic in the spectrum, but for parts
where the harmonics are buried in the noise floor, it will be a
noise peak.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities will create distortion
products at sum and difference frequencies of mfa ± nfb where
m, n = 0, 1, 2, 3, etc. Intermodulation terms are those for which
neither m nor n are equal to zero. For example, the second order
terms include (fa + fb) and (fa – fb), while the third order terms
include (2 fa + fb), (2 fa – fb), (fa + 2 fb) and (fa – 2 fb).
The AD7898 is tested using the CCIF standard where two input
frequencies are used. In this case, the second and third order
terms are of different significance. The second order terms are
usually distanced in frequency from the original sine waves,
while the third order terms are usually at a frequency close to the
input frequencies. As a result, the second and third order terms
are specified separately. The calculation of the intermodulation
distortion is as per the THD specification where it is the ratio of
the rms sum of the individual distortion products to the rms
amplitude of the fundamental expressed in dBs.
AD7898
4
, V
5
, and V
Signal to (Noise + Distortion) = (6.02 N + 1.76) dB
1
THD
is the rms amplitude of the fundamental, and V
6
(
are the rms amplitudes of the second through the
dB =
S
/2 and excluding dc) to the rms value of the
)
20
log
V
2
2
+
V
3
2
+
V
V
1
S
4
2
/2), excluding dc.
+
V
5
2
+
V
6
2
2
, V
3
,
–6–
Relative Accuracy
Relative accuracy or endpoint nonlinearity is the maximum
deviation from a straight line passing through the endpoints of
the ADC transfer function.
Differential Nonlinearity
This is the difference between the measured and the ideal
1 LSB change between any two adjacent codes in the ADC.
Positive Full-Scale Error (AD7898-10)
This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal (4 × VREF – 3/2 LSB) after the
Bipolar Zero Error has been adjusted out.
Positive Full-Scale Error (AD7898-3)
This is the deviation of the last code transition (01 . . . 110 to
01 . . . 111) from the ideal (VREF – 3/2 LSB) after the Bipolar
Zero Error has been adjusted out.
Bipolar Zero Error (AD7898-10, AD7898-3)
This is the deviation of the midscale transition (all 0s to all 1s)
from the ideal AGND – 1/2 LSB.
Negative Full-Scale Error (AD7898-10)
This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal (–4 × VREF + 1/2 LSB) after Bipo-
lar Zero Error has been adjusted out.
Negative Full-Scale Error (AD7898-3)
This is the deviation of the first code transition (10 . . . 000 to
10 . . . 001) from the ideal (–VREF + 1/2 LSB) after Bipolar
Zero Error has been adjusted out.
Track/Hold Acquisition Time
Track/Hold acquisition time is the time required for the output
of the track/hold amplifier to reach its final value, within
± 1/2 LSB, after the end of conversion (the point at which the
track/hold returns to track mode). It also applies to situations
where there is a step input change on the input voltage applied
to the V
wait for the duration of the track/hold acquisition time after the
end of conversion, or after a step input change to V
starting another conversion to ensure that the part operates to
specification.
PSR (Power Supply Rejection)
Variations in power supply will affect the full-scale transition,
but not the converter’s linearity. Power Supply Rejection is the
maximum change in full-scale transition point due to change in
power-supply voltage from the nominal value.
IN
input of the AD7898. This means that the user must
IN
, before
REV. A