AD7322 Analog Devices, AD7322 Datasheet - Page 14

• Manufacturer Part Number: AD7322
• Description: Software Selectable True Bipolar Input, 2-Channel, 12-Bit Plus Sign ADC
• Manufacturer: Analog Devices

Specifications of AD7322

• Resolution (bits): 13bit
• # Chan: 2
• Sample Rate: 1MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Bip,Diff-Uni,SE-Uni
• Ain Range: Bip (Vref),Bip (Vref) x 2,Bip (Vref) x 4,Bip 10V,Bip 2.5V,Bip 5.0V,Uni (Vref) x 4,Uni 10V
• Adc Architecture: SAR
• Pkg Type: SOP

AD7322
Channel-to-Channel Isolation
Channel-to-channel isolation is a measure of the level of crosstalk
between any two channels. It is measured by applying a full-scale,
100 kHz sine wave signal to all unselected input channels and
determining the degree to which the signal attenuates in the
selected channel with a 50 kHz signal. Figure 14 shows the worst-
case across all eight channels for the AD7322. The analog input
range is programmed to be the same on all channels.
Intermodulation Distortion
With inputs consisting of sine waves at two frequencies, fa and
fb, any active device with nonlinearities creates distortion
products at the sum and difference frequencies of mfa ± nfb,
where m, n = 0, 1, 2, 3, and so on. Intermodulation distortion
terms are those for which neither m nor n are equal to 0. For
example, the second-order terms include (fa + fb) and (fa − fb),
whereas the third-order terms include (2fa + fb), (2fa − fb),
(fa + 2fb), and (fa − 2fb).
The AD7322 is tested using the CCIF standard where two input
frequencies near the top end of the input bandwidth are used.
In this case, the second-order terms are usually distanced in
frequency from the original sine waves, whereas the third-order
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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
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.
PSR (Power Supply Rejection)
Variations in power supply affect the full-scale transition but
not the linearity of the converter. Power supply rejection is the
maximum change in the full-scale transition point due to a
change in power supply voltage from the nominal value (see the
Typical Performance Characteristics section).
CMRR (Common-Mode Rejection Ratio)
CMRR is defined as the ratio of the power in the ADC output
at full-scale frequency, f, to the power of a 100 mV sine wave
applied to the common-mode voltage of the V
frequency, f
where Pf is the power at frequency f in the ADC output, and Pf
is the power at frequency f
CMRR (dB) = 10 log (Pf/Pf
S
, as
S
in the ADC output (see Figure 17).
S
)
IN
+ and V
IN
−
S