AD7356 Analog Devices, AD7356 Datasheet - Page 11

• Manufacturer Part Number: AD7356
• Description: Differential Input, Dual, Simultaneous Sampling, 5 MSPS, 12-Bit, SAR ADC
• Manufacturer: Analog Devices

Specifications of AD7356

• Resolution (bits): 12bit
• # Chan: 2
• Sample Rate: 5MSPS
• Interface: Ser,SPI
• Analog Input Type: Diff-Uni
• Ain Range: (Vref) p-p,2.048 V p-p
• Adc Architecture: SAR
• Pkg Type: SOP

Total Harmonic Distortion (THD)
THD is the ratio of the rms sum of harmonics to the
fundamental. For the AD7356, it is defined as
where:
V
V
through the sixth harmonics.
Spurious Free Dynamic Range (SFDR)
SFDR is the ratio of the rms value of the next largest component
in the ADC output spectrum (up to f
the rms value 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 a noise peak.
Intermodulation Distortion (IMD)
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, and so on. Intermodulation distortion terms
are those for which neither m nor n is equal to zero. For example,
the second-order terms include (fa + fb) and (fa − fb), while the
third-order terms include (2fa + fb), (2fa − fb), (fa + 2fb), and
(fa − 2fb).
1
2
, V
is the rms amplitude of the fundamental.
THD
3
, V
4
, V
( )
dB
5
, and V
=
−
20
6
are the rms amplitudes of the second
log
V
2
2
+
V
3
2
S
+
/2 and excluding dc) to
V
V
1
4
2
+
V
5
2
+
V
6
2
Rev. A | Page 11 of 20
The AD7356 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 and 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 sum of the fundamentals expressed in decibels.
Thermal Hysteresis
Thermal hysteresis is defined as the absolute maximum change
of reference output voltage after the device is cycled through
temperature from either
Thermal hysteresis is expressed in ppm using the following
equation:
where:
V
V
or T_HYS–.
REF
REF
(25°C) is V
(T_HYS) is the maximum change of V
T_HYS+ = +25°C to T
T_HYS– = +25°C to T
V
HYS
(
ppm
REF
)
=
at 25°C.
V
REF
(
25
MIN
MAX
°
V
C
to +25°C
REF
to +25°C
)
−
(
V
25
REF
°
C
(
T
)
_
REF
HYS
at T_HYS+
)
×
AD7356
10
6